Poor Hole Cleaning Research Articles

Study of Rheological Characteristics of a Water-Based Drilling Fluid in Presence of Biopolymers, Synthetic Polymer, and Modified Natural Polymer

The major contemplation in the recent decades is to minimize the operational difficulties during any drilling activity by improving the characteristics of water-based drilling fluids (WBDF). Such problem as a poor hole-cleaning because of settling of drill cutting and debris are extremely common. This problem will eventually convert into a serious non-productive time event in the form of pipe sticking. The most common additives added in the mud system to improve its rheological properties and tackle sedimentation issues are polymeric materials. During this study, four different polymers including sodium alginate and pure-bore as biopolymers, PHPA as a synthetic polymer, and the L-grade polyanionic cellulose (PAC-L) as a modified natural polymer have been used to improve rheological characteristics of WBDF. Laboratory measurements have indicated no considerable changes in the mud weight in the case of addition of these polymers. Moreover, these results reveal that all the systems behave as shear thinning fluid (flow index 1). A decrease in the dynamic viscosity with an increase in the shear rate has been observed for all samples. The disentangling of polymeric chains occurring at high shear rate eventually reduces the viscosity of these systems. In addition, samples that comprised of pure-bore and sodium alginate exhibit the desired operating magnitude of rheology (PV, YP, GS, AV, and YP/PV). These results show such particles minimize operational problems arising because of a poor hole-cleaning. In contrast, a system with PHPA and PAC-L has shown detrimental rheological characteristics. The high molecular weight of PHPA and the hydration of PAC-L in the presence of potassium chloride decrease their performance.

FACILITATING MUD DESIGN, CEMENTING JOB DESIGN AND THE ENTIRE DRILLING OPERATIONS BY MODELLING THE RHEOLOGICAL PROPERTIES OF WATER-BASED MUD AND OIL-BASED MUD WITH TEMPERATURE

The increasing rental cost of drilling Rig and the associated painful cost of downtime during drilling operations are some of the major concerns of the oil & gas companies. Improper rheological properties of drilling mud may cause a variety of problems including insufficient cuttings transport, limited solids suspension, poor hole-cleaning and excess filtrate loss into the formation. Facilitating mud design, cementing job design and the entire drilling operations will save Rig time and associated cost and prompt management of oil & gas companies to devote more of their useful time and resources to other significant aspects of their operations. The aforesaid prompted this work to invent a method for developing mathematical models representing the rheological parameters of drilling mud (water-based mud and oil-based mud) to enable prediction of the rheological properties in emergency situations where and when Laboratory services are not immediately available. The methods applied include Laboratory testing and mathematical modelling. Results revealed that the mathematical models can be confidently applied to predict the Plastic viscosity and Yield stress of water based mud and oil-based mud as the correlation coefficient (R-squared value) obtained for each of the aforesaid rheological properties was higher than 95% Therefore, as the rheological properties of water-based mud and oil-based mud depend on their composition, physical and chemical properties, mathematical models should be proactively developed for the Plastic viscosity and Yield stress for every mud in hole to enable prediction of the its rheological parameters when and where laboratory services are not immediately available.

Applications of Machine Learning Methods to Predict Hole Cleaning in Horizontal and Highly Deviated Wells

Summary Machine learning (ML) has become a robust method for modeling field operations based on measurements. For example, wellbore cleanout is a critical operation that needs to be optimized to enhance the removal of solids to reduce problems associated with poor hole cleaning. However, as wellbore geometry becomes more complicated, predicting the cleaning performance of fluids becomes more challenging. As a result, optimization is often difficult. Therefore, this research focuses on developing a data-driven model for predicting hole cleaning in deviated wells to optimize drilling performance. More than 500 flow loop measurements from eight studies are used to formulate a suitable ML model to forecast hole cleanout in directional wells. Measurements were obtained from hole-cleaning experiments that were conducted using different loop configurations. Experiments ranged in test-section length from 22 to 100 ft, in hole diameter from 4 to 8 in., and in pipe diameter from 2 to 4.5 in. The experiments provided measured equilibrium bed height at a specific flow rate for various fluids, including water-based and synthetic-based fluids and fluids containing fibers. Several relevant test parameters, including fluid and cutting properties, well inclination, and drillstring rotation speed (drillpipe rev/min), were also considered in the analysis. The collected data have been analyzed using the Cross-Industry Standard Process for Data Mining. This paper is unique because it systematically evaluates various ML models for their ability to describe hole cleanout processes. Six different ML techniques: boosted decision tree (BDT), random forest (RF), linear regression, multivariate adaptive regression spline (MARS), neural networks, and support vector machine (SVM) have been evaluated to select the most appropriate method for predicting bed thickness in a wellbore. Also, we compared the predictions of the selected ML method with those of a mechanistic model for cases without drillstring rotation. Finally, using the ML model, a parametric study has been conducted to examine the impact of various parameters on the cleanout performance of selected fluids. The results show the relative influence of different variables on the prediction of cuttings bed. Accordingly, flow rate, drillpipe rev/min, and fluid behavior index have a strong impact on dimensionless bed thickness, while other parameters such as fluid consistency index, solids density and diameter, fiber concentration, and well inclination angle have a moderate effect. The BDT algorithm has provided the most accurate prediction with an R2 of 92%, a root-mean-square error (RMSE) of 0.06, and a mean absolute error (MAE) of roughly 0.05. A comparison between a mechanistic model and the selected ML technique shows that the ML model provided better predictions.

Stuck Pipe Detection in Geothermal Operation with Support Vector Machine

One of the biggest problems during drilling operation is a stuck pipe in which the drill string would stick or freeze in the well. This challenge leads to a significant amount of remedial costs and time. Many researchers have investigated different factors regarding the stuck pipe. These factors include poor hole cleaning, improper mud design, key seating, balling up of bit, accumulation of cutting and caving, poor bottom hole assembly configuration, differential pressure, etc. (Chamkalani, Pordel Shahri, and Poordad 2013). Since geothermal drilling targets lost circulation zones at reservoir depth, the chance of getting stuck pipe events becomes higher. Many publications reported that lost circulation events that lead to stuck pipe events have become the top non-productive time (NPT) contributor to costs in many geothermal drilling projects. The consequences of a stuck pipe are very costly, that include lost time when releasing the pipe, time and cost of fishing out the parted Bottom Hole Assembly (BHA), and efforts to abandon the tool(s) in the hole. Despite many observations that have been done to develop a system in avoiding stuck pipe incidents in oil and gas drilling operations using artificial intelligence (AI), few works have been developed for geothermal drilling operations. In this research, we propose a method to build an early warning system model for stuck pipe conditions based on a Support Vector Machine. Based on the experiment result Support Vector Machine Algorithm showed good performance with 89% accuracy and 81% recall for limited training dataset.

Dynamically Evaluating the Performance of Naturally Occurring Additives to Control Lost Circulation: On the Effect of Lost Circulation Material Type, Particle-Size Distribution, and Fracture Width

Summary Lost circulation is one of the most challenging problems during drilling of oil and gas wells. This issue leads to significant loss of drilling fluid, increase of nonproductive time as well as dictating additional costs to drilling companies. Lost circulation may also lead to other consequences, including stuck pipe, poor hole cleaning, and well control issues. How to efficiently control lost circulation have been traditionally depending on the type of the used lost circulation material (LCM). Injection of commonly available materials (without any further process on their chemical properties) into the thief zone is a common method of lost circulation control. These nonmodified materials are named as conventional LCMs against the unconventional LCMs which are designed/produced just for fluid lost control. The objective of this paper is to comparatively investigate the performance of cane, oak shell, wheat, and mica as LCM of water-based drilling fluid exposed to fractured formations. These materials were chosen because of their low cost, easy access, and compatibility with the environment. The sealing efficiency of these materials was assessed at different particle-size distributions (PSDs) for proper treatment of loss circulation. To do so, an experimental setup containing a cell with adjustable fracture size was designed. Among the LCM formulations made of each of the materials, oak shell formulations are better than the others, followed by mica and cane blends, respectively. The results reveal that combining the materials together is a better treatment than the separate use of them. As it will be seen in detail later, high diversity in particle size (broad PSD) causes more efficient control of fluid loss. Also, to reduce the dependency of sealing ability of LCM formulation on fracture size, mixing of the materials with different particle sizes and shapes is recommended.

Pilot-scale study on the suspension of drill cuttings: Effect of fiber and fluid characteristics

Drilling operation smoothness is essential to minimize drilling non-productive time (NPT). Inadequate cuttings transport can result in cuttings bed build-up in the wellbore low side, jeopardizing the whole drilling operation. Modifying base fluid properties can prevent the associated risks with poor hole cleaning. Fiber sweeps enhanced hole-cleaning performance and increased cuttings transport to the surface with a negligible increase in fluid viscosity. This experimental investigation examines the effect of fibers on the cuttings carrying capacity of carboxyl methylcellulose (CMC) based polymeric fluids. The carrying capacity of the fluids is assessed by measuring the suspended and deposited cuttings/solids concentrations after a predefined quiescent period. Synthetic monofilament fiber of 0.9 specific gravity, 100 μm diameter, and two different lengths (3 and 12 mm) were used. Polymer concentrations were 0.747 and 1.1 wt %, while fiber concentration was varied from 0.00 to 0.08 wt%. The investigation was performed using a vertically configured annular test section (150 cm long) with a rotating inner shaft speed. Experimental results indicate that increasing fiber or/and polymer concentrations significantly improved cuttings carrying capacity of the fluids in suspending fine (1 mm) particles.In most cases, the carrying capacity of the fluids in suspending coarse cuttings (3 and 6 mm particles) was slightly improved with the addition of polymer and fiber. Although the rotation of the inner shaft substantially reduced the deposition of fine particles but did not prevent the settling of coarse cuttings. In addition, short fibers demonstrated better performance than long ones in improving the carrying capacity of the fluids. Utilizing long and short mixed fibers at a specific proportion improved the cuttings carrying capacity of the fluid better than unmixed fiber.

Experimental study on water-based mud: investigate rheological and filtration properties using cupressus cones powder

Improper drilling fluid parameters may induce a variety of issues, including insufficient cuttings transport, limited solids suspension, poor hole cleaning, and excessive filtrate invasion to the formation. Controlled and optimized drilling fluids rheology is considered the key parameter to solve severe drilling problems encountered during drilling operations. Oil-based muds have numerous applications, but owing to some economic, environmental, and operational challenges, drilling companies are looking for new additives to enhance the characteristics of water-based muds for improved performance. However, the longer exposure of some WBM additives degrades them, which leads to insignificant mud characteristics. In this study, micro-sized naturally occurring agro-material namely cupressus cones powder (CCP) has been assessed as a potential additive in WBM for the first time to enhance the mud performance by improving its rheological and filtration properties. The objective of this study is to prepare a drilling fluid using abundantly available cupressus cones powder and investigate its effects on mud properties. The rheological and filtration characteristics of the drilling muds were determined based on API standards. A series of experiments have been performed to evaluate the impact of CCP loading on the rheology and fluid loss characteristics of drilling mud. The concentration of CCP was varied from 1 to 7 ppb. The findings of rheological characteristics demonstrated that altering the CCP loading enhanced the plastic viscosity, yield point, and gel strength of water-based drilling mud. The optimal concentration for PV was recorded in the range of 2–4 ppb, while the optimum value of YP was obtained at 6 ppb. Moreover, the temperature affected the viscosity and filtration of the mud, whereas the CCP containing muds were found salt resistant. The percent decrease in filtrate volume at 25, 121, and 150 °C was noted as 50, 59.6, and 62%, respectively. The effectiveness of the CCP was also observed from the SEM analysis. This study described the use of a locally available agro-waste material as a potential mud additive.

Experimental and numerical study of cuttings transport in inclined drilling operations

Directional drilling has become popular in recent decades in both onshore and offshore operations due to reduced drilling costs and improved recovery. In a directional well drilling operation, drill cuttings tend to settle down at the lower side of the inclined annular section. If the generated cuttings are not removed from the hole section properly, it causes a cuttings bed formation in the annular section. Different drilling related problem such as poor rate of penetration, excessive torque and drag, increase differential sticking often associated with a poor hole cleaning which eventually lead to increase in non-productive time (NPT). Therefore, the success of inclined well drilling operation largely depends on effective cleaning of drill cuttings from the annular section. A variety of parameters, including the fluid rheology, mud velocity, cuttings size, drill pipe rotation and drill pipe inclination generally influence the cuttings transport performance. Optimization of these drilling parameters is crucial to ensure proper hole cleaning. In this study, a Computational Fluid Dynamics (CFD) model for the inclined well section is used to investigate the cuttings transport efficiency (CTE). An Eulerian-Eulerian multiphase flow model is proposed and validated with lab scale experimental data. The experiments were performed in a 6.16-m-long annular test section having an outer pipe diameter of 4.5-inch and an inner pipe diameter of 2.5-inch. The setup is equipped with Electrical Resistance Tomography (ERT) system to measure the instantaneous solid volume fraction and a visualization section. A non-Newtonian Heschel-Bulkley (HB) fluid was used as drilling mud and solid glass beads of 2.50 mm–3.00 mm were used as cuttings in the experiment. This study shows a good agreement in visualization of mechanistic three-layer model of cuttings transport in terms of ERT data from experiment and CFD simulation. The validated CFD model is used to perform 5- Factors factorial design and analysis of variance (ANOVA) study. ANOVA shows that the interaction effects of mud velocity-cuttings size, mud velocity-inclination are statistically significant. Finally, this study proposed a statistical model to estimate the CTE of an inclined well considering the two factor and three factor interactions among the variables. Also, the model shows that drill pipe rotation has negligible effect in improving cuttings transport efficiency in the inclined well. The proposed model also reveals that cuttings size and fluid velocity account for 78% contribution in the transport efficiency for an inclined well. Furthermore, an Artificial Neural Network (ANN) method is used to verify the contribution of lower order interaction in the statistical model. Though empirical model shows few lower order two factor interactions (fluid rheology -cuttings size, fluid rheology-inclination), and three factor interactions (velocity-cuttings size-inclination, fluid rheology-cuttings size-inclination); ANN model shows that lower order interaction are significant in model prediction and should not be ignored. The findings of this study can help in better understanding the interaction behaviour among drilling parameters and optimized cuttings transport efficiency in the inclined drilling operation for a wide variety drilling parameters.

Integrated 3D Mechanical Earth Modelling to Intensively Investigate the Wellbore Instability of Zubair Oil Field, Southern Iraq

Wellbore instability in the Zubair oil field is the main problem in drilling operations. This instability of the wellbore causes several problems including poor hole cleaning, tight hole, stuck pipe, lost circulation, bad cementing, and well kick or blowout that lead to an increase in the nonproductive time. This article aims to set up an appropriate drilling plan that mitigates these instability issues for further well drilling. Field data from six wells (logs, drilling and geological reports as well as offset well tests) were used to build a one-dimensional mechanical earth modeling for each well. The constructed model of selected wells was combined to construct the three-dimensional mechanical earth modeling, which can enable the distribution of all estimated geomechanical parameters along the field of interest. The results revealed that the strip slip and normal faults are the common fault regimes in Zubair oil field located in carbonate rocks and clastic rocks, respectively. The Mogi-Coulomb failure criterion is conservative in determining the minimum and maximum mud weight, and it agrees with the determination of real failure from the image/and caliper logs. The best direction to drill the deviated and horizontal wells was towards the minimum horizontal stress with 140o azimuth from the north. The recommended ranges of mud weight along the sections of 12.25" and 8.5" of the highly deviated and horizontal wells were (between 1.46 and 1.58 gm/cm3) without any expected wellbore instability problems. Based on the outcomes of 3D model, it is expected that the wellbore instability issues are most likely to occur in the domes of; Shauiba and Hamma and in formations; Tanuma, Khasib and Nahr-Umr. In contrast the less wellbore instability problems are expected to expose in Rafidya dome. The study presents an appropriate mud window that can be used to design to minimize the wellbore stability problems when new wells will be drilled in Zubair oil field.

MoS2 Nanoparticle Effects on 80 °C Thermally Stable Water-Based Drilling Fluid.

Bentonite-based drilling fluids are used for drilling, where inhibitive fluids are not required. The rheological and the density properties of the drilling fluids are highly affected by high temperature and pressure. Due to high temperature, the clay particles stick together, and the fluid system becomes more flocculated. Poorly designed drilling fluid may cause undesired operational issues such as poor hole cleaning, drill strings sticking, high torque and drag. In this study, the 80 °C thermally stable Herschel Bulkley’s and Bingham plastic yield stresses drilling fluids were formulated based on lignosulfonate-treated bentonite drilling fluid. Further, the impact of a MoS2 nanoparticle solution on the properties of the thermally stable base fluid was characterized. Results at room temperature and pressure showed that the blending of 0.26 wt.% MoS2 increased the lubricity of thermally stable base fluid by 27% and enhanced the thermal and electrical conductivities by 7.2% and 8.8%, respectively.

Comprehensive Experimental Investigation of Hole Cleaning Performance in Horizontal Wells Including the Effects of Drill String Eccentricity, Pipe Rotation, and Cuttings Size

Abstract Extended reach drilling (ERD) wells with a horizontal and highly deviated section are widely applied in the oil and gas industry because they provide higher drainage area than vertical wells and hence increase the productivity or injectivity of the well. Among many issues encountered in a complex well trajectory, poor hole cleaning is the most common problem, which occurs mainly in the deviated and horizontal section of oil and gas wells. There are significant parameters that have a serious impact on hole cleaning performance in high-angle and horizontal sections. These include flowrate, rheology, and density of the drilling fluid, drill string eccentricity, pipe rotation, and cuttings size. It has been recognized that the action of most of these parameters to transport drilled cuttings is constantly a point of controversy among oilfield engineers. In the present study, extensive experiments were conducted in an advanced purpose-built flow rig to identify the main parameters affecting on circulate the cuttings out of the test section in a horizontal position. The flow-loop simulator has been designed to allow easy variation of operational parameters in terms of flowrate, mud density, drill string eccentricity, pipe rotation, and cuttings size. In addition, the study covers the impacts of laminar, transition, and turbulent flow regimes. The goal of such variation in the operational conditions is to simulate real-field situations. The results have shown that drill string rotation and flowrate were the operational parameters with the highest positive influence on the cuttings transports process. In contrast, drill pipe eccentricity has a negative influence on cuttings removal efficiency. The cuttings transportation performance is further improved by pipe rotation at different levels of eccentricity, especially at fully eccentric annuli. It was also shown that larger cuttings appeared to be easier to remove in a horizontal annulus than smaller ones. The experimental results would provide a more in-depth understanding of the relationship between drilling operation parameters and hole cleaning efficiency in ERD operations. This will help the drilling teams to realize what action is better to take for efficient cutting transportation.

Hole-Cleaning Fibers Improve Cuttings-Carrying Capacity

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 203147, “Investigating Hole-Cleaning Fibers’ Mechanism To Improve Cutting Carrying Capacity and Comparing Their Effectiveness With Common Polymeric Pills,” by Mohammad Saeed Karimi Rad, Mojtaba Kalhor Mohammadi, SPE, and Kourosh Tahmasbi Nowtarki, International Drilling Fluids, prepared for the 2020 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, held virtually 9–12 November. The paper has not been peer reviewed. Hole cleaning in deviated wells is more challenging than in vertical wells because of the boycott effect or the eccentricity of the drillpipe. Poor hole cleaning can result in problems such as borehole packoff or excessive equivalent circulating density. The complete paper investigates a specialized fibrous material (Fiber 1) for hole-cleaning characteristics. The primary goal is to identify significant mechanisms of hole-cleaning fibers and their merits compared with polymeric high-viscosity pills. Hole-Cleaning Indices Based on a review of the literature, most effective parameters regarding hole cleaning in different well types were investigated. These parameters can be classified into the following five categories: - Well design (e.g., hole angle, drillpipe eccentricity, well trajectory) - Drilling-fluid properties (e.g., gel strength, mud weight) - Formation properties (e.g., lithology, cutting specific gravity, cuttings size and shape) - Hydraulic optimizations (e.g., flow regime, nozzle size, number of nozzles) - Drilling practices (e.g., drillpipe rotation speed, wellbore tortuosity, bit type, rate of penetration, pump rate) In this research, rheological parameters and parameters of the Herschel-Bulkley rheological model are considered to be optimization inputs to increase hole-cleaning efficiency of commonly used pills in drilling operations. The complete paper offers a detailed discussion of both the importance of flow regime and the role of the Herschel-Bulkley rheological model in reaching a better prognosis of drilling-fluid behavior at low shear rates. The properties of the fibrous hole-cleaning agent used in the complete paper are provided in Table 1. Test Method Two series of tests were performed. The medium of the first series is drilling water, with the goal of evaluating the efficiency of Fiber 1 in fresh pills. The second series of tests was per-formed with a simple polymeric mud as a medium common in drilling operations. Formulations and rheological properties of both test series are provided in Tables 4 and 5 of the complete paper, respectively.

Improving hole cleaning in horizontal wells by using nanocomposite water-based mud

Efficient cuttings transport is important for achieving safe and successful drilling operations. However, poor hole cleaning is considered to be one of the main issues that happens frequently in horizontal and highly deviated wells. The selection of the drilling fluids with enhanced rheological properties is one of the effective methods to increase cuttings transportation efficiency. The major purpose of the present research is to investigate the application of silica (SiO2) nanoparticles in improving hole cleaning in extended reach drilling (ERD) operations. Nanocomposite drilling fluids were prepared by adding silica nanoparticles into water-based mud (WBM) at different weight percent concentrations (0.1–1.5 wt%). The flow loop experiments were performed on a sophisticated purpose-built flow rig by circulating the tested fluid samples into the test section in a horizontal position, considering the influence of drill pipe rotation, flow rates, cuttings sizes, mud density, and drill pipe eccentricity. In addition, the study covers the impacts of laminar, transition, and turbulent flow regimes. The goal of such variation in the operational parameters is to simulate real field conditions. The results indicated that the addition of the silica nanoparticles to WBM increases the colloidal interactions with cuttings, therefore leading to a substantial enhancement in cuttings removal efficiency especially with the higher concentration of silica nanoparticles. It was shown that nanoparticles in drilling fluid increase cuttings transport by 20.32%–32.75% for different nanocomposite water-based drilling fluids used in this study. The proposed investigation demonstrates the feasibility of using silica nanoparticles in WBM to enhance the capability of drilling fluids in transporting and circulating drilled cuttings out of the wellbore. Furthermore, the results of this project would provide a more reliable understanding of the relationship between drilling operation parameters and hole cleaning performance in ERD operations.

Experimental Investigation of Aloe-Vera-Based CuO Nanofluid as a Novel Additive in Improving the Rheological and Filtration Properties of Water-Based Drilling Fluid

SummaryDrilling technology in petroleum engineering is associated with problems such as high fluid loss, poor hole cleaning, and pipe sticking. Improvement of rheological and filtration properties of water-based drilling fluids (WDFs) plays a major role in resolving these drilling problems. The application of nanotechnology to WDF in the recent past has attracted much attention in addressing these drilling operations problems. In the present work, we investigate the application of natural aloe vera and CuO nanofluids combined as an additive in WDF to address the drilling problems. The nanofluids of three different concentrations of CuO nanoparticle (0.2, 0.4 , and 0.6 wt%) with aloe vera as a base fluid are prepared for this study by adopting a two-step method. The prepared nanofluids are characterized by their particle size and morphological characteristics. Conventional WDF (DF.0) is synthesized, and the prepared aloe-vera-based CuO nanofluid is added to the WDF to prepare nanofluid-enhanced water-based drilling fluid (NFWDF) of different concentrations of nanoparticles, namely, 0.2 , 0.4, and 0.6 wt%. The prepared drilling fluid mixture is then characterized for its rheological and filtrate loss properties at various temperatures. Thermal stability and aging studies are performed for both WDF and NFWDF. The experimental results are then modeled using rheological models. The results reveal that aloe-vera-based CuO nanofluids improve the thermal stability and rheological properties of drilling fluid and significantly decrease the American Petroleum Institute (API) filtrate. Viscosity for WDF shows an approximately 61.7% decrease in heating up to 90°C. Further, the hot roll aging test causes a 63% decrease in the viscosity of WDF at 90°C. However, the addition of aloe-vera-based CuO nanofluids is found to aid in recovering the viscosities to a great extent. The fluid loss values before hot rolling are observed to be 6.6 mL after 30 minutes, whereas fluid loss values for the NFWDFs are found to be 5.9, 5.4, and 4.6 mL, respectively. The fluid loss value after hot rolling for the WDF is found to be 10.8 mL after 30 minutes, whereas fluid loss values for the NFWDFs are found to be 9.2, 8.5, and 7.7 mL, respectively. The rheological performance data of NFWDF project a better fit with the Herschel-Bulkley model and suggest improvement in rheological and filtration properties. There has been limited research work available in understanding the impact of aloe-vera-gel-based nanofluids in improving the performance of WDFs through the improvement of its rheological and filtration properties. This study aims to exploit the property of native aloe vera and CuO nanofluids combined together to enhance the rheological and filtration properties of WDF by conducting the tests both before and after hot rolling conditions. This study acts as an important precursor for developing novel additives for WDF to improve its rheological and filtration properties. This study is also expected to benefit the industry and solve the major challenges in deep-well drilling operations and high-pressure and high-temperature (HPHT) drilling operations.

Real-Time Prediction of Equivalent Circulation Density for Horizontal Wells Using Intelligent Machines.

Equivalent circulation density (ECD) is an important part of drilling fluid calculations. Analytical equations based on the conservation of mass and momentum are used to determine the ECD at various depths in the wellbore. However, these equations do not incorporate important factors that have a direct impact on the ECD, such as bottom-hole temperature, pipe rotation and eccentricity, and wellbore roughness. This work introduced different intelligent machines that could provide a real-time accurate estimation of the ECD for horizontal wells, namely, the support vector machine (SVM), random forests (RF), and a functional network (FN). Also, this study sheds light on how principal component analysis (PCA) can be used to reduce the dimensionality of a data set without loss of any important information. Actual field data of Well-1, including drilling surface parameters and ECD measurements, were collected from a 5–7/8 in. horizontal section to develop the models. The performance of the models was assessed in terms of root-mean-square error (RMSE) and coefficient of determination (R2). Then, the best model was validated using unseen data points of 1152 collected from Well-2. The results showed that the RF model outperformed the FN and SVM in predicting the ECD with an RMSE of 0.23 and R2 of 0.99 in the training set and with an RMSE of 0.42 and R2 of 0.99 in the testing set. Furthermore, the RF predicted the ECD in Well-2 with an RMSE of 0.35 and R2 of 0.95. The developed models will help the drilling crew to have a comprehensive view of the ECD while drilling high-pressure high-temperature wells and detect downhole operational issues such as poor hole cleaning, kicks, and formation losses in a timely manner. Furthermore, it will promote safer operation and improve the crew response time limit to prevent undesired events.

Real-time drilling optimisation – driving drilling excellence

Here we explore a real-time solution that anticipates drilling events and avoid delays caused by such issues as poor hole cleaning, higher torque and drag, swab and surge, stuck pipe, lost circulation, formation damage and wellbore instability. This is important if drilling optimisation is a major technical and corporate goal or if you wish to go beyond the traditional approach of collecting real-time data only to monitor operations. The presented state-of-the-art ‘real-time drilling optimisation’ solution creates a dynamic, real-time picture of the entire wellbore and key drilling variables and parameters using advanced, tightly coupled thermodynamic, hydraulic and mechanical drilling models and trend analysis applications to anticipate potential drilling issues in real-time while drilling. The solution can also be used to perform scenario based ‘what-if’ analysis and ‘look-ahead’ simulations of drilling operation with the purpose to analyse outcome of alternative operating scenarios. This is an effective solution that simplifies real-time data analysis by using trends and deviations between modelled and actual data to predict changing wellbore conditions and developing a digital twin of a wellbore. This paper includes robotic drilling automation, aimed at reducing invisible loss time, enhancing drilling efficiency and safety by applying operational safeguards to the drilling control system, providing automatic safety mechanisms and enabling automatic sequences. This paper highlights technical cases demonstrating how this analytic solution not only auto-detects symptoms (which can lead to drilling events or hazards, invisible loss time and non-productive time) but also optimises drilling performance through simulation well ahead of time, thus driving drilling efficiency.

Aerated Drilling Optimization in Geothermal Well Drilling in Field “X” Cluster “Y”

Aiming for productive fault in Suban Agung Rim, Field X Cluster Y Bengkulu Province, Indonesia, PT Pertamina Geothermal Energy (PGE) drilled some wells to discover the potential awaited. However there are challenge awaits each meter ahead especially in reservoir sections where loss circulation is expected. Knowing the risk, PGE decided to drill the well utilizing aerated drilling. The method has known for decades to be the most effective approach in dealing loss circulation. The method applies certain value of compressed air to be injected in fluid stream, so bubbling process can be achieved in order to reduce the mud weight. The method has benefit to maintain ROP and minimize the risk for pipe get stuck due to poor hole cleaning in fractured formation. There are three wells drilled in Field X Cluster Y which has the same problem in 9-7/8” section; all experienced stuck pipe while drilling. During the process aerated drilling was utilized, however it was not sufficient. This paper will discuss and explain on how the occurrence happened and what to do next in similar condition to avoid the problems.

Simulation Study on Influences of Wellbore Tortuosity on Hole Cleaning in Extended-Reach Drilling

Summary Wellbore tortuosity or spiraling can lead to the trapping of a cuttings bed in a trough of a tortuous hole, thereby leading to poor hole cleaning in extended-reach drilling. The objectives of this study included quantitatively evaluating the influences of wellbore tortuosity on hole cleaning and cuttings-transport behavior in extended-reach drilling. In addition, the study provided a recommendation of effective drilling practices. The study involved performing hole-cleaning-optimization studies for an extended-reach well with a long horizontal section aiming for maximum reservoir contact, by use of a transient cuttings-transport simulator. The planned trajectory of the well was assumed to have a certain degree of wellbore tortuosity in the horizontal section. The pump rate and bottoms-up circulation operation were optimized on the basis of parameter studies and additional transient simulations by considering the effects of penetration rate and variation in cuttings size. Simulation results indicated the formation of a considerably high cuttings bed, particularly in the downdip intervals (updip in mud-flow direction) at an insufficient pump rate; one-third to one-half of the drillpipe diameter could be potentially buried in a cuttings-deposit bed, and this can result in a packed-off hole or stuck pipe. A higher rate of penetration (ROP) can also cause insufficient hole cleaning. In this case, controlled drilling that maintains a reasonably low penetration rate may be effective. Furthermore, borehole breakout may enlarge hole diameter and generate large-sized cuttings. Both of these can have negative impacts on hole cleaning, and, thus, borehole stability and smooth wellbore-trajectory controls should be carefully considered. To clean these holes, frequent bottoms-up circulations were effective at each stand of drilling even if the optimization of other drilling parameters was limited. The findings also revealed that accumulated cuttings in a tortuous wellbore were trapped in the trough of the hole, and that the bed height of locally trapped cuttings in the downdip intervals could be much higher than that indicated by previous studies.

Innovative Tool Improves Hole-Cleaning Efficiency in Extended-Reach Wells

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 175165, “Use of an Innovative Tool To Improve Hole-Cleaning Efficiency in Extended-Reach Wells in Saudi Arabia,” by Mike Okot, Marlio Campos, German Muñoz, and Alawi G. Alalsayednassir, Saudi Aramco; Matt Weber, Frank’s International; and Zahid Muneer, SPE, Schlumberger, prepared for the 2015 SPE Kuwait Oil and Gas Show and Conference, Mishref, Kuwait, 11–14 October. The paper has not been peer reviewed. Saudi Aramco operates a large offshore oilfield development that has driven achievements in multilateral and extended-reach directional wells. One challenge the operator faces is to maintain proper hole cleaning in extended 8½-in. tangent sections at 85–87° inclinations, which are drilled in excess of 10,000 ft. In an effort to drill efficiently, a new technology to increase cuttings removal was trial tested on Well A1 from an onshore location of the field. Introduction Historically, drilling very long tangent sections required the use of several tandem sweep pills, wiper trips, and reaming and back reaming to maintain hole quality and remove cuttings from the wellbore efficiently. Poor hole cleaning can lead to tight intervals, increased torque and drag, and, eventually, stuck pipe. Extended-reach Well A1 was drilled to a measured depth (MD) of 30,480 ft [8,650-ft true vertical depth (TVD)] into a stratigraphic environment composed of limestone, shale, and siltstone. The objective of the trial test for the tool was to improve the drilling efficiency. To obtain the best possible hole cleaning, a simulation was performed by placing the new tools every three stands along the tangent section in the 8½-in.-hole section. The goals of the trial test were To enhance hole cleaning by removal of cuttings To reduce the frequency and number of tandem sweep pills To reduce the frequency and number of wiper trips To reduce torque and drag levels and make them comparable with those of offset wells To reduce drilling cost Well A1 resumed drilling from a preset 9?-in.-casing point in December 2013 in the Manifa field. The well was drilled from surface to 30,480-ft MD and into a stratigraphic environment composed of limestone, sandstone, and siltstone. The objective was to hold vertical from surface to 1,535 ft, build up to 85° from 1,535 to 11,659 ft, and hold an 85–90° inclination to total depth. The challenges were to clean hole while drilling the long 8½-in. tangent section from 11,659 to 24,160 ft. To address these challenges, the tool company recommended the use of 5-in. cuttings-bed- impeller (CBI) tools at a frequency of one tool per three stands on the 5-in. drillpipe. The 8½-in. tangent section was drilled smoothly without any hole-cleaning issues (no tight hole or stuck pipe). The primary hole cleaning was achieved during drilling, and no secondary hole cleaning was required. A service company installed a cuttings-flowmeter system at the shakers to evaluate hole-cleaning efficiency and performance of the hole-cleaning tools.

Effect of Nanofluids of CuO and ZnO in Polyethylene Glycol and Polyvinylpyrrolidone on the Thermal, Electrical, and Filtration-Loss Properties of Water-Based Drilling Fluids

Summary The challenges in drilling problems such as formation damage, pipe sticking, lost circulation, poor hole cleaning, and fluid loss need better solutions. Nanotechnology, by means of nanofluids, provides potential solutions for the development of improved water-based mud (WBM). This work presents the use of nanofluids of CuO and ZnO prepared in various base fluids, such as xanthan gum, polyethylene glycol, and polyvinylpyrrolidone (PVP), which are commonly used in oilfield operations, for the development of nanofluid-enhanced drilling mud (NWBM). In this paper, formulations of various nanofluids with varying concentrations of nanoparticles, such as 0.1, 0.3, and 0.5 wt%, were investigated for their effect on the thermal, electrical, and fluid-loss properties of NWBM. In addition, these results also were compared with those obtained with microfluids of CuO and ZnO for the microfluid-enhanced drilling mud (MWBM) to understand the effect of particle size. It is observed that the use of nanofluids in WBM helps to improve their thermal properties, with an associated direct impact on their cooling efficiency at downhole and surface conditions compared with those using microfluid. Filtration-loss and filter-cake-thickness studies on WBM, MWBM, and NWBM were also carried out with an American Petroleum Institute (API) filter press. It is observed that the fluid loss decreases with addition of the nanofluids and microfluids in WBM, with nanofluids showing an improved efficacy over microfluids. The studies, in general, bear testimony to the efficacy of nanofluids in the development of next-generation improved water-based drilling fluids suitable for efficient drilling.