Mud Viscosity Research Articles

Optimization of hydraulic structure and well flushing parameters of a truncated cone drill bit for drilling shaft sinking

ABSTRACT Based on a research method combining numerical simulations and model testing, a numerical model and test platform for gas lift reverse circulation multiphase coupling in well washing were developed. The hydraulic structure and well washing parameters of a φ5 m truncated cone bit used in the Beifeng well at Taohutu Coal Mine were optimized, and the distribution law of the well washing flow field was determined. The findings revealed that: (1) with a bit taper of 40 and a length-diameter ratio of 0.32 for the truncated cone, the hydraulic structure was optimal. Compared with the original bit structure, the axial speed of mud at the slag suction port increased by 15.9%, and the average sliding speed of mud at the inclined rock surface increased by 63.2%. (2) The multiphase fluid in the slag discharge pipe flowed successively in the form of “low-speed stable two-phase flow” and “high-speed disordered three-phase flow,” while the multiphase fluid in the horizontal and inclined bottom holes flowed predominantly in radial and tangential patterns, respectively. (3) The optimal parameter combination for efficient well washing with the truncated cone bit included a bit rotation speed of 8 r/min, a gas injection rate of 5600 m3/h, an air duct sinking ratio of 0.79, and a mud viscosity of 176 mPa·s, with bit rotation speed being the most significant factor affecting effective washing efficiency. These results could provide a valuable reference for improving the efficiency of drilling and well flushing in Jurassic strata of western China.

Drilling liquid from plant based oil using carbon based nanoparticles

The risks of disposal associated with using mineral-based drilling liquids have prompted the search for alternatives. Despite their long-standing use in the industry, mineral-based liquids pose challenges due to their eco-toxicity, poor biodegradability, and low fire resistance. Recently, vegetable-based liquids have gained attention for their excellent environmental friendliness and high fire resistance. In this study, a green drilling liquid was developed from non-food grade vegetable oil. The base liquid was extracted and the oil underwent epoxidation to enhance the thermal stability. Two different carbon-based nanoparticles were synthesized from coconut shells and graphite. The graphene nanoparticles derived from graphite exhibited a higher surface area compared to those from coconut shells. The properties of the developed graphene nanomud, such as gel strength, thermal conductivity, specific gravity, mud viscosity, mud filtrate properties, cutting carrying index, electrical conductivity, and toxicity, were investigated and compared with diesel-based nanomud. Results showed that neem graphene nanomuds possess properties that are comparable to, and in some cases better than diesel-based oil mud. The addition of 0.25 wt% to 2.0 wt% of graphene nanoparticles increased the electrical conductivity of the fluid from 58.7 to 229.5 µS/cm at 25 °C, enabling the use of resistivity imaging techniques for wellhole geological studies. Additionally, the nanofluids demonstrated desirable thermal conductivity, ranging from 0.138 W/m·K to 0.267 W/m·K at 25 °C, making them suitable coolants. Furthermore, toxicity tests using bean plants demonstrated that graphene-based nanomuds are environmentally friendly and could offer a cleaner, more sustainable option for drilling operations.

CFD–DEM method is used to study the multi-phase coupling slag discharge flow field of gas-lift reverse circulation in drilling shaft sinking

To elucidate the distribution law of the multiphase coupling slag discharge flow field in gas-lift reverse circulation during drilling shaft sinking, a numerical analysis model of gas–liquid–solid multiphase coupling slag discharge was established by CFD–DEM (Coupling of computational fluid dynamics and discrete element method) method, taking the drilling of North Wind well in Taohutu Coal Mine as an example. This model presented the distribution of the multiphase flow field in the slag discharge pipe and at the bottom hole, and was validated through experimentation and theoretical analysis. Finally, the impact of factors, including bit rotation speed, gas injection rate, air duct submergence ratio, and mud viscosity on the slag discharge flow field was clarified. The results indicated that the migration of rock slag at the bottom of the well was characterized by “slip, convergence, suspension, adsorption, and lifting”. The slag flow in the discharge pipe exhibited the states of “high density, low flow rate” and “low density, high flow rate”, respectively. The multiphase fluid flow patterns in the well bottom and slag discharge pipe were horizontal and axial flows, respectively. The model test of the gas lift reversed circulation slag discharge and the theoretical model of the bottom hole fluid velocity distribution confirmed the accuracy of the multiphase coupling slag discharge flow field distribution model. The rotation speed of the drill bit had the most significant impact on the bottom hole flow field. Increasing the rotation speed of the drill bit can significantly enhance the tangential velocity of the bottom hole fluid, increase the pressure difference between the bottom hole and annular mud column, and improve the adsorption capacity of the slag suction port. These findings can provide valuable insights for gas lift reverse circulation well washing in western drilling shaft sinking.

On Improving Water-Based Drilling Mud Swelling Control Using Modified Poly(Vinyl Alcohol)s.

One of the most challenging issues when drilling under high-temperature, high-pressure (HT/HP) conditions is wellbore instability caused by clay swelling and fluid loss of the drilling mud. One of the most difficult issues when drilling under high-temperature, high-pressure (HT/HP) conditions is wellbore instability caused by clay swelling and fluid loss in drilling mud. Two modified PVOHs, nonionic and cationic polymers made from sodium bentonite clay and deionized water at concentrations of 0.08, 0.28, and 0.49 wt.%, were introduced to WBM percent. A series of specific gravity and mud rheology experiments at 25, 55, and 85 °C indicated that both values drop monotonically with increasing temperature, regardless of PVOH addition or concentration. A temperature increase of 30 °C decreases the mud viscosity of WBM (without PVOH) by 18% from its starting value, on average. Only 0.1% of cationic and nonionic polymer reduces viscosity by 10% and 0%, respectively. Experimenting with mud samples for 5 h revealed that adding nonionic polymers enhances mud filtration by up to 34.7%, 1.25 times more than that achieved from cationic polymers under the same filtration circumstances. Increasing the filtration temperature moderately affects mud cake generation due to increased mud swelling index and preferential adsorption by nonionic polymer. The latter observation was corroborated by determining the polymer content of the filtrates. Therefore, it was shown that nonionic polymers adsorbed more (118.9 mg/g) than cationic polymers (84.51 mg/g). Increased filtration temperature moderately affects mud cake generation due to increased mud swelling index and preferential adsorption by nonionic polymer. The latter observation was corroborated by testing the filtrates for the polymer content. As a result, it was discovered that nonionic polymer adsorbed more (118.9 mg/g) than cationic polymer (84.51 mg/g). Thermogravimetry analysis (TGA) finally tested the thermal stability of polymers.

A Study on the Borehole Wall Stability Analysis and Slurry Ratio Optimization for Construction of Pile in Complex Marine Strata.

In order to address the issue of hole collapse, which frequently arises when boring piles are being constructed in intricate marine strata, this paper discusses the influence of the slurry ratio on the slurry performance as well as the mechanism of slurry wall protection. It performs this by means of theoretical analysis, laboratory ratio testing, engineering analogies, numerical simulation, and field testing. Our findings demonstrate that adding sodium polyacrylate and sodium carboxymethyl cellulose can enhance mud's viscosity, contribute to flocculation, and improve the connection between mud and soil layers. Refering similar engineering cases, three optimization schemes are proposed for achieving a mud ratio that offers wall protection in complex marine strata. Furthermore, the particle flow model of slurry viscous fluid is established. The collapse of holes in the sand layer is reflected in the uneven radial displacement of hole walls and the invasion of mud particles. Increasing the viscosity of mud gradually transforms the uneven radial deformation of pore walls in the sand layer into a uniform radial deformation, whereas increasing the proportion of mud significantly decreases the radial displacement of hole walls. Additionally, when the mud pressure in the hole is 300 kPa and 600 kPa, the wall protection effect is better, and there is no particle penetration by substances such as sand. It is found that a high mud pressure can promote the diffusion of mud particles into the sand layer, while low mud pressure cannot balance the pressure on deep soil. The results of the field tests show that the ratio of water-clay-bentonite-CMC-Na-sodium carbonate = 700:110:90:1.5:0.5 used (where the mass percentage of each material is 77.8% water, 12.2% clay, 10% bentonite, 0.16% CMC-Na, and 0.05% sodium carbonate) can effectively prevent hole collapse and reduce the thickness of the sand layer at the bottom of the hole by 50%.

Laboratory Study on Vallejo and Scovazzo’s Methods in Estimating the Rheology Parameters of Bentonite and Kaolinite Muds

The mud undrained shear strength and viscosity are the essential parameters in understanding the behavior of mudflow. One of the laboratory test methods to estimate the undrained shear strength and viscosity is Vallejo and Scovazzo’s cylinder strength meter test (CSMT) and flume channel test, respectively. This paper compares the undrained shear strength of kaolin and bentonite muds obtained from the CMST to those obtained using the fall cone and mini vane shear tests and also studies the scale effects in the flume channel test in measuring the mud viscosity at a 20o to 40o slope angles and at various liquidity indexes. The results exhibit that CMST could estimate the undrained strength of mud as low as 0.45 kN/m2 with a liquidity index of up to 5.93. Then, the reduction of the size of the flume channel by half resulted in a mud viscosity of about 2.3 times higher.

Explicit Data-Based Model for Predicting Oil-Based Mud Viscosity at Downhole Conditions.

One of the functions of drilling mud is to transport cuttings out of a drilled well. To fulfill this purpose, the mud must possess optimal viscous characteristics. The main goal of this study is to develop a model for estimating the plastic viscosity (PV) of oil-based muds (OBMs) at downhole conditions, especially when high-temperature, high-pressure wells are drilled. Existing methods used by previous researchers include the following: the multiplicative factor method, the relative dial readings approach, and the nonlinear regression technique. These methods do not result in flexible, generalizable, accurate, or robust models. Furthermore, existing literature mostly contains models that are only applicable under normal temperature and pressure conditions (surface conditions). To overcome these challenges, this study employed the artificial neural network (ANN) technique to predict the PV of OBM under downhole conditions. The data used to develop the model consists of 88 OBM laboratory PV measurements obtained from literature. The findings indicate that the performance of the developed model using the statistical metrics of means square error (MSE), root-mean-square error (RMSE), and correlation coefficient (R) was 0.0185, 0.136, and 0.967 respectively. To test for the generalizability of the developed model, a new data set consisting of 56 data points was used. In this regard, the model had an R value of 0.80, an MSE of 0.95, and an RMSE of 0.975. In order to ascertain the parametric importance of the inputs, a connection weight algorithm was utilized. In this regard, the downhole pressure had a higher influence on the PV (64.5%) than that of downhole temperature (35.5%). To make the models simple to incorporate in software applications, they were explicitly presented. In terms of memory requirements and processing speed for software applications, the models had a memory footprint of 48 bytes and required 12 floating-point operations to give an output. This model is valid for 20 °C ≤ temperature ≤315 °C and 0 psi ≤ pressure ≤40,000 psi. The characteristics of the models proposed in this work for which originality is claimed include the models' computational cost evaluation, their explicitness, and a suggestion for using them in the field. Upon utilizing the proposed models, time-consuming laboratory measurements of PV would no longer be necessary, and real-time results could be provided in the field.

Modelling of fluid mud flow based on a three-dimensional hydrodynamic model : incorporating a 3D rheological model

Modeling fluid mud in estuaries and coastal areas is a complicated task due to its non-Newtonian characteristics. A continuous modeling approach was adopted to investigate the laminar flow of fluid mud, with a three-dimensional (3D) form of the Herschel–Bulkley rheological model introduced into the finite volume coastal ocean model (FVCOM) to calculate the apparent viscosity of fluid mud. The model was validated against two flume experiments for the laminar flow of fluid mud. The results showed that the developed model was capable of accurately reflecting the continuous distribution of velocity and density from the near-bottom to the upper water column. Based on the validated model, the difference between the 3D rheological model and a 1DV rheological model on the simulation results was assessed. The study found the results of the 1DV model and the 3D model show obvious differences. This illustrates the significant effect of apparent viscosity in horizontal direction taken into account by the 3D rheological model.

Исследования поверхностной и адсорбционной активности модифицированного лигносульфонатного реагента для регулирования параметров бурового раствора

The possibility of obtaining a modified lignosulfonate reagent based on acrylic and lignosulfonate components is considered. To study the effect of electrolytes on the surface activity of a complex reagent based on acrylic and lignosulfonate components, the surface tension of aqueous solutions of inorganic salts of NaCl and CaCl2 of different concentrations was determinedwith the introduction of 0.1 to 2% of the reagent. The assessment of adsorption activity was carried out on the basis of constructingan isotherm of surface tension at the liquid-liquid interface under static conditions in time at a constant concentrationof the reagent. The possibility of a modified lignosulfonate reagent to effectively reduce the conditional viscosity of clay drilling mud in the temperature range from 20 to 180°C has been established.

Mathematical modelling of drilling mud plastic viscosity at downhole conditions using multivariate adaptive regression splines

Viscosity is an essential mud property which enables it to transport cuttings out of a well. Determining the real time value of mud viscosity at downhole conditions is complex and till date lacks a precise model. Literature is filled with models that are only applicable at surface conditions with most of the models being artificial neural network (ANN) based. Neural networks have been criticized for their long training time because they rely on a trial-and-error approach to determine their optimal architecture. The few models related to mud viscosity at downhole conditions are based on non-linear regression which are not flexible in nature. However, Multivariate Adaptive Regression Splines (MARS) has at no time been used notwithstanding some of its known benefits over ANN and other regression methods. The focus of this study is to model mud plastic viscosity at downhole conditions with the MARS method using parameters such as temperature, pressure and initial mud viscosity. MARS is a flexible non-parametric splines-based technique that extends linear regression models by including nonlinearities and interactions between predictors. An experimental database comprising 88 and 149 data points culled from literature for oil-based mud (OBM) and water-based mud (WBM) respectively were utilized for developing the models. For each mud type, the most suitable model was determined by choosing the model with the maximum coefficient of determination (R2) value and the least values of mean square error (MSE), root mean square error (RMSE), and generalized cross-validation criterion (GCV). Using these criteria, the R2, MSE and RMSE of the MARS models according to the mud type were found to be 0.64, 104.35, 10.21 and 0.71, 12.8, 3.57 for OBM and WBM respectively while the GCV values were 129.3 and 14.38 for OBM and WBM respectively. Due to lack of mud rheology data at downhole conditions, it was difficult to compare the performance of the developed models with existing models. Parametric importance analysis indicate that temperature has the highest effect on mud viscosity estimation at downhole conditions. The developed models are valid for 20 °C ≤ Temperature ≤315 °C and 0 psi ≤ Pressure ≤40,000 psi. This pioneer work on using MARS in drilling fluid property prediction points out the implementation protocol, the dataset utilized, the relative importance of input variables and the explicit model for estimating mud viscosity at downhole conditions.

Volumetric Changes of Mud on Mars: Evidence From Laboratory Simulations

AbstractSubtle mounds have been discovered in the source areas of Martian kilometer‐sized flows and on top of summit areas of domes. These features have been suggested to be related to subsurface sediment mobilization, opening questions regarding their formation mechanisms. Previous studies hypothesized that they mark the position of feeder vents through which mud was brought to the surface. Two theories have been proposed: (a) ascent of more viscous mud during the late stage of eruption and (b) expansion of mud within the conduit due to the instability of water under Martian conditions. Here, we present experiments performed inside a low‐pressure chamber designed to investigate whether the volume of mud changes when exposed to a Martian atmospheric pressure. Depending on the mud viscosity, we observe a volumetric increase of up to 30% at the Martian average pressure of ∼6 mbar. The reason is that the low pressure causes instability of the water within the mud, leading to the bubble formation that increases the volume of the mixture. This mechanism bears resemblance to the volumetric changes associated with the degassing of terrestrial lava or mud volcano eruptions caused by a rapid pressure drop. We conclude that the mounds associated with putative Martian sedimentary volcanoes might indeed be explained by volumetric changes in the mud. We also show that mud flows on Mars and elsewhere in the Solar System could behave differently to those found on Earth because mud dynamics are affected by the formation of bubbles in response to the different atmospheric pressures.

Investigation of Preparation of Slag Wool from Melting-Separated Red Mud

The preparation of high-quality inorganic fibers by centrifugation from modified melting-separated red mud, which is the product of the efficient recovery of pig iron from red mud, is a new approach to achieve large-scale production of high value-added materials from red mud. This method has a wide range of application prospects and could contribute substantially to the comprehensive utilization of bulk industrial solid waste and the development of a circular economy. In this study, melting-separated red mud was modified with water-quenched blast furnace slag, quartz sand, and quicklime. The effect of the CaO/Na2O mass ratio on the viscosity, fluidity, and crystallization performance of the melting-separated red mud was investigated; slag wool was prepared by centrifugation under laboratory conditions; and the effect of the CaO/Na2O mass ratio on the morphology and properties of the slag wool was investigated. The viscosity of modified melting-separated red mud with different CaO/Na2O mass ratios shows a decreasing trend with increasing temperature, and the fluidity increases with increasing temperature, indicating that the melt fluidity is improved. The suitable fiber-forming temperature of the melting-separated red mud shows a trend of increasing–decreasing–increasing with an increasing CaO/Na2O mass ratio, and at a CaO/Na2O ratio of 3.0, the maximum suitable fiber-forming temperature is 81 °C. Considering the feasibility of slag wool preparation from modified melting-separated red mud, the CaO/Na2O of the modified raw material system should not be higher than 3.0. The crystallization temperature of modified melting-separated red mud with different CaO/Na2O mass ratios first increases and then decreases, with a peak of 1450 °C at a CaO/Na2O ratio of 4.0. Slag wool prepared from modified melting-separated red mud with different CaO/Na2O mass ratios exhibits good properties, with a diameter of 5.47–6.67 µm and a slag ball content of 2.7–8.4%.

Investigation Into Local Additives as Substitute to Standard Viscosifier; Advances in Drilling Technology

In Nigeria, drilling companies import a bulk of drilling fluid materials that they use to carry out their respective operations. This has been a major concern to oil and gas industries since these drilling fluid materials cannot be recycled, are highly expensive in terms of foreign exchange, are not environmentally friendly, not very effective, and non-biodegradable. This work presents an experimental investigation into the reliability of the use of local materials as a substitute to conventional viscosifiers. Local materials used in the analysis are mucuna solannie (Ukpo), brachystegia eurycoma (Achi), and detarium microcarpium (Ofo). The results obtained from the experimental analysis show that they compared closely to the standard viscosifer formulated with Pac-R. The results showed that the density, specific gravity, pH, yield stress, gel strength, plastic viscosity, and yield point of mud formulated from local materials compared favorably with that of the imported viscosifier. An increase in concentration of the local sample also favoured its potential to replace the Pac-R. In terms of cost, cutting carrying ability, and positive environmental impacts, the local materials could serve the Nigerian drilling company better.

Utilization of mesoporous nano-silica as high-temperature water-based drilling fluids additive: Insights into the fluid loss reduction and shale stabilization potential

Optimally performing drilling fluids play a vital role in drilling operations. The demand for thermally stable drilling fluid in the oil and gas sector necessitates using advanced additives to create suitable formulations. This research study introduces the novel application of Mesoporous Nano-Silica (MNS) to enhance water-based drilling fluid's inhibitive, rheological, and fluid loss characteristics. MNS was synthesized by the sol-gel technique with Cetyltrimethylammonium Bromide (CTAB) for generating the pores. The hydrodynamic particle size of the synthesized MNS was 134.47 nm with a stable zeta potential of −32.2 meV. Brunauer-Emmett-Teller (BET) analyzer estimated the specific surface area to be 626 m2/g and the pore volume to be 0.3415 cm3/g. A comparative analysis of the drilling fluid properties is presented in which MNS was added to the fixed base formulation at varied concentrations (0.05, 0.1, 0.2, 0.5, and 1 wt%). Samples were subjected to hot rolling at 180 °C temperatures at 100 psi pressure for 16 h, evaluating the influence of thermal aging on the properties of the drilling fluid. The viscometric investigation was performed at 25 and 70 °C while the inhibitive properties were checked via shale recovery test and capillary suction timer. The filtration properties were examined at 100 psi and 500 psi pressure at 150 °C. The experimental findings reveal that MNS can substantially improve the thermal properties of water-based drilling fluids, maintaining rheological characteristics and drastically reducing fluid loss while imparting some inhibitive properties. Interestingly, after hot rolling the plastic viscosity of MNS-infused mud was 77% better than that of the base mud. Incorporating macro-sized particles and MNS nanoparticles into water-based drilling fluids can enhance its rheological properties, reduce filtrate loss, and improve shale inhibition characteristics which may be attributed to either the size effect or the synergistic influence of materials. Therefore, including MNS as a high-performance additive may contribute to advancing drilling operations in the petroleum industry, offering valuable insights for optimizing drilling fluid formulations.

Influence of drilling mud pulsations on well cleanout efficiency

Purpose. Determination of the influence of the non-stationary flow regime of the drilling mud on the efficiency of cleaning the wellbore in the annulus from drill cuttings. Methodology. The study on the carrying capacity of the drilling mud in a laboratory installation is carried out by simulating the process of its pulsations at different frequencies. The choice of the studied frequencies was made on the basis of previous studies. The evaluation of the influence of factors on the efficiency of rock removal was carried out using Latin experimental plans, which allowed us to evaluate the influence of the selected factors with a minimum number of experiments without losing the quality of the result. Findings. The influence of factors (mud flow rates, eccentric placement of the drill string, plastic viscosity of the drilling mud, pulsation frequency, rotation of the drill string) on the efficiency of cuttings removal along the annular space of the wellbore is analyzed. Three factors with the best interaction were found, which made it possible to build dependencies of their influence on the efficiency of rock removal on the surface. The effect of changing the frequency of pulsations of the drilling mud has been studied, and graphical dependences of their influence on the decrease in the volume of rock particles in the annular space have been obtained. Originality. Based on the results of experimental studies, the effectiveness of the impact of drilling mud pulsations on cleaning the well from rock particles has been proven. Practical value. The effectiveness of the use of drilling mud pulsations for hydrotransportation of cuttings along the horizontal section of the wellbore has been confirmed.

Oil-based drilling mud comprising biosurfactant and hydrophobic zinc nano-powders with excellent H2S scavenging performance

Hydrogen sulfide (H2S) could be released during the drilling operations of oil and gas wells. The release of this lethal gas to the surface will expose the working personnel to high safety and health risks. Additionally, the contact of this very corrosive gas with handling and processing equipment will result in severe economic losses. Despite such serious issues, formulating and testing oil-based muds (OBMs) with H2S scavenging capability is still lacking in the literature. Thus, the key aim of this study is to formulate invert emulsion diesel-based drilling mud (abbreviated as IEDBM) that is capable of effectively scavenge H2S in-situ once it is encountered. This aim is realized through the addition of a small quantity of potassium permanganate to the formulated IEDBM. According to the obtained results, the inclusion of a small amount of potassium permanganate (i.e., 1 wt.%) can scavenge up to 0.43 and 0.71 kg H2S per barrel of the formulated mud at the breakthrough (i.e., 29.8 h) and saturation (i.e., 86.2 h) times, respectively. The IEDBM was stabilized using Span 80 (a non-ionic surfactant) and rhamnolipid anionic biosurfactant. The IEDBM also comprised hydrophobic zinc nano-powders (contact angle with water ∼105⁰) as weighting agent. The application of rhamnolipid biosurfactant and hydrophobic zinc nano-powders in drilling formulations is another novel aspect of the work reported herein. The shear rate-shear stress data were well fitted using the Bingham plastic, Casson, and Herschel–Bulkley models. The apparent viscosity of the IEDBM was investigated under different shear rates and the obtained results showed a sharp drop in the mud apparent viscosity with increasing the shear rate up to 40 s−1, followed by a slower decrease upon the further increase in the applied shear rate; which is in line with those of OBMs reported in the literature. The effect of temperature on the apparent viscosity of the IEDBM was also investigated; the change in the mud viscosity was found to be inversely proportional to temperature in almost a linear fashion. The results presented in this work reveal the high potential of formulating OBMs with effective H2S scavenging performance and appropriate flow properties.

Hydraulic parameters optimization of two-stage PDC bit in deep formation applications

Two-stage PDC (Polycrystalline diamond compact) bit is a special drilling bit consisting of a small-diameter pilot and a large-diameter reamer. The unique rock-breaking structure is designed to improve drilling efficiency and reduce drilling costs in deep and abrasive formations. According to previous studies, the hydraulic structure of the two-stage PDC bit can significantly affect the drilling performance of removing cuttings near the bottom of the wellbore. Therefore, this research has proposed to achieve high efficiency of cuttings removal by optimizing the hydraulic structure. In this paper, the flow field at the bottom of the well near the two-stage PDC bit (Φ171.45 mm pilot + Φ215.9 mm reamer) has been numerically studied using the finite element method. As shown in the analysis results, both the flow rate of the pilot and the flow rate ratio of the pilot to the reamer increase significantly with the increase of the area ratio of the pilot nozzles to the total nozzles. The numerical data supports that the cuttings can be removed effectively from the bottom of the wellbore when the area ratio is between 0.75 and 0.80. Moreover, the cuttings can be removed effectively from the bottom of the wellbore when the mud viscosity is about 10 mPa s, the rate of penetration is between 4 and 8 m/h, the drill speed is 90 rpm, and the cuttings particle sizes is between 1 and 2 mm. Besides, increasing the pump rate can improve the cutting-carrying efficiency through the wellbore bottom. Field test results indicate that the average penetration rate of the optimized bit is increased by 47.17% and the footage of the optimized bit is increased by 95.40% compared to the equivalent formation in adjacent wells. This study can provide guidance for the optimal design of the hydraulic structure of such two-stage PDC bits.

Experimental and factorial design analysis of viscosity and fluid loss control of water-based mud treated with pineapple leaves

Experimental and factorial design analysis of viscosity and fluid loss control of water-based mud treated with pineapple leaves

Drilling Heat Maps for Active Temperature Management in Geothermal Wells

Summary Geothermal energy has gained much attention as a promising contributor to the energy transition for its ability to provide a reliable, environmentally friendly source of heat and baseload power. However, drilling high-temperature (HT) reservoirs presents significant technical and economic challenges, including thermally induced damage to bits and downhole (DH) tools, increasing drilling time and cost. This paper introduces drilling heat maps for proactive temperature management in geothermal wells during well planning and real-time drilling operations phases to avoid thermally induced drilling problems. This study uses a transient hydraulic model integrated with a thermal model to predict the bottomhole circulating temperature (BHCT) while drilling geothermal wells. The model is used to generate a large volume (1,000s) of case scenarios to explore the impact of various cooling and other heat management strategies on the BHCT in the Utah FORGE field, used here as an example, covering a wide range of drilling parameters. Results are captured, visualized, and analyzed in convenient heat maps, illustrating the advantages of using such heat maps in geothermal well construction and real-time operations. Model validation with FORGE 16A(78)-32 well data and a west Texas case scenario shows good agreement between the modeling results and experimental data, with a mean absolute percentage error (MAPE) of less than 4%. There is a clear logarithmic relationship between the drilling flow rate and BHCT at a constant mud inlet temperature and a linear relationship between the mud inlet temperature and BHCT at a constant drilling flow rate. Pronounced variation of BHCT in geothermal wells is observed with mud type, mud weight, and mud viscosity. In addition, insulated drillpipe (IDP) technology is found to significantly reduce BHCT (14–44% on average for FORGE scenarios) compared to conventional drillpipe (CDP), particularly in wells with extended measured depth (MD) where other heat management technologies and strategies become less effective. Drilling heat maps can alert drilling engineers to strategies with the highest BHCT-lowering impact, allowing focused technology selection and decision-making regarding optimal temperature management during the geothermal well design phase. In addition, real-time heat maps are valuable for facilitating active temperature management and providing real-time guidance for optimal drilling parameters during daily drilling operations. In general, heat maps can help to avoid drilling problems related to the combination of HT and temperature limitations of DH equipment, which will benefit the safe and cost-efficient development of geothermal resources.

Mud loss behavior in fractured formation with high temperature and pressure

Drilling into fractured formations can easily lead to mud loss, which significantly affects drilling efficiency and increases drilling costs. In high-temperature and high-pressure environments, changes in mud properties render mud loss more uncontrollable. On the basis of a mud performance test in a high-temperature and high-pressure environment, and considering the time-varying characteristics of wellbore temperature and pressure and the distribution law of fracture temperature and pressure, a coupling model of temperature and pressure in the wellbore and fracture was established in this study. The developed model was solved numerically using the finite difference approximation, and the characteristics of the mud loss were analyzed. The effects of geothermal gradient, fracture parameters (fracture width, fracture length, and deformation capacity), mud properties (viscosity, yield value, and specific heat capacity), and operating conditions on mud loss were investigated. The model was validated using field measurement-while-drilling tool data of the LD1 well in the South China Sea. The results show that the average errors between the calculated temperature and pressure results of the numerical model and the actual data are 2.45% and 0.57%, respectively, which proves that the model has high accuracy in the prediction of the bottom hole temperature and pressure. A comparison of the predicted data of mud loss with the actual measured data indicates that the average error of the mud leakage model is 4.23%. This also demonstrates that the model has a high accuracy in predicting mud loss. In addition, the results show that the mud performance changes significantly under high-temperature and high-pressure conditions, which has a significant influence on mud loss. The geothermal gradient affected the mud properties and thus significantly affected the mud loss characteristics. The larger the mud pumping rate, the larger the bottomhole pressure difference and the more serious the mud loss. Blindly increasing mud viscosity is not advisable because it may lead to more serious losses. With an increase in the mud yield value, the mud flow resistance in the fractures can be significantly increased to inhibit mud loss. The larger the mud-specific heat capacity, the less mud loss is affected by the temperature. With an increase in the fracture width, the degree of mud loss gradually decreased. The larger the fracture length and deformation capacity, the more serious the mud loss. The fracture length and width could be inverted using the developed model.