Oil-based Mud Research Articles

Experimental Investigation on the Effect of Methane Solubility in Oil-Based Mud Under Downhole Conditions

Accurate prediction of CH4 solubility in oil-based mud is significant for evaluating gas kick severity and implementing proper well control. The main factors affecting gas solubility in oil-based drilling fluid are base oil content, pressure, temperature, drilling fluid viscosity, and the components in natural gas. This work tests the complete series of solubility of high-purity CH4 in oil-based mud simulating downhole conditions on a 5,000-m-deep well relative to temperature, pressure, viscosity, and base oil content with temperature ranging from 40°C to 140°C and pressure ranging from 2 to 56 MPa using a PVT autoclave. Then, the effects of temperature, pressure, base oil content, and drilling fluid viscosity on the test target are analyzed using multiple experimental data processing methods. It is found that the variation of methane solubility with pressure and temperature are almost linearly under interested ranges. The effects of pressure (0.205 to ~0.294%/MPa) are much higher than that of temperature (–0.008 to –0.011%/°C) in oil-based drilling mud; the solubility of methane decreases as viscosity increases. Models for predicting methane solubility have been developed using screening procedures and statistics regression, which can be integrated into gas-liquid flow models to investigate flow behavior while gas kicking.

Looking into the Reservoir: Performance Evaluation of Fractured Long Horizontal Wells Using of Borehole Imaging Logs

Field G is a highly fractured and faulty field, this paper is seeking about the necessity to keep running Image logs in new oil wells and how the interpretation of the results would led the team to completing wells optimally and to design our well completion properly to prevent high initial water cut. Learnings are summarized from 40+ image logs ran in this field over the last few years. A cross field G seismic interpretation confirmed on lapping reservoirs and 3 major fault trends with different transmissibility. Also, sseismic and sub seismic Faults and fractures are confirmed from BHI with a NE-SW strike of field G and can be possibly related to production behavior of some wells. In 2015, field G Water Encroachment Study was conducted to identify the cause of high initial water cut of producers. It proposed that detecting fractures early via under-balanced drilling, Borehole Imaging Tools (BHI) and sealing the conduits with production packers would help reduce initial water-cuts [2]. BHI tools are open hole tools that measure either electrical conductivity of the borehole wall or the sonic travel time and amplitude. Micro-conductivity or amplitude and travel time measurements generate an image that shows bedding, fractures and many other fine-scale features. Acoustic tools are preferred in Oil Based Mud (OBM) system and hence they have not been used in field G to the extent that it required a dedicated discussion.

In-Situ Visualization and Characterization of Filter-Cake Deposition Using Time-Lapse Micro-CT Imaging

This work establishes and verifies a laboratory method for accurate, noninvasive, and nondestructive in-situ measurement of filter-cake, or mudcake, properties using high-resolution X-ray microcomputed tomography (micro-CT). Accurate in-situ characterization of mudcake properties is of vital importance for understanding mudcake deposition during mud-filtrate invasion and, more broadly, the deposition of filter cake during industrial filtration processes. The developed laboratory method involves the injection of pressurized drilling mud into a borehole located at the center of a cylindrical rock core sample. Radial mud-filtrate invasion is induced by maintaining the outside of the core sample at a lower pressure. Mudcake is deposited on the borehole wall while mud filtrate flows into the surrounding pore space of the core sample. Simultaneously, the core sample is continuously scanned using high-resolution X-ray micro-CT, allowing for three-dimensional (3D) in-situ visualization and characterization of the deposited mudcake. Analysis of experimental results is aided by a new set of filtration equations that are generalized for use with either water-based mud or invert emulsion drilling fluids, such as oil- or synthetic oil-based mud. Each experiment produces a time-series data set consisting of injected mud volume and the corresponding in-situ average mudcake thickness, porosity, and permeability. Results are presented for experiments involving injection of water- and synthetic oil-based drilling mud. We observe that experimental measurements agree well with modeled results when mudcake is thin compared to the size of the borehole—a condition that would be satisfied under most normal field conditions. Initial results also suggest that the developed method may be capable of providing accurate in-situ 3D measurements of local filter-cake properties during compressible cake filtration, which has significant implications for a wide range of industrial applications.

Realistic Simulation of Multiphase Kick Tolerance Model Promotes Safer Well Control Operations: Case Study

Nowadays, deep-water drilling is of great importance for the development of oil and gas production. It is necessary to determine the maximum pressure that the formation can withstand during well control operation. This value can be calculated using several variables, including kick tolerance. The purpose of this study is to analyze a real well control event using dynamic well control modeling software that calculates the kick tolerance based on the single-phase and multiphase dispersed kick (gas) model. The initial results show that the type of drilling fluid plays an important role in the calculation of the kick tolerance. The calculated kick tolerance using a single-phase model indicates an allowable kick volume of 56 barrels (bbls), but in reality, we had a dispersed gas kick in a synthetic oil-based mud (SOBM) drilling fluid, which requires special kick tolerance calculations based on a multiphase dynamic model. After reviewing the results of the multiphase kick tolerance simulation, it was found that the maximum gas kick volume is more than twice that of using a single-phase model in an oil-based mud drilling fluid, allowing safe well control operations and reducing the possibility of accidents.

Cleaning Functional Spacer for Improving Sealing Integrity and Zonal Isolation of Cement Sheath in Shale Gas Wells: Laboratory Study and Field Application

Summary Maintaining sealing integrity of cement sheath is essential to oil and gas well completion. The development of large-scale hydraulic fracturing reservoir stimulation technology in recent years has put forward higher requirements for the sealing integrity of cement sheath. For horizontal shale gas wells, it is often necessary to clean the oil-based mud (OBM) before pumping cement slurry to ensure sufficient contact and bonding of cement slurry to casing and formation. Therefore, the removal efficiency of OBM determines the cementation quality of cement slurry with casing and formation. The present work implements and evaluates a novel cleaning functional spacer (CFS) to overcome OBM removal difficulty through laboratory experiments. CFS consists of weighted spacer (CFS I) and chemical preflush (CFS II). CFS I and CFS II both contain chemical washing agent. OBM removal efficiency test results suggest that with the increase of the concentration of chemical washing agent, the removal efficiency of OBM increases, and the increase of temperature will promote the removal of OBM. Also, it can be found that OBM that sticks to the casing is easier to remove than OBM that sticks to the simulated permeable formations. The water drop on an oil-wet surface gives a contact angle of 66.15°, as nonwetting behavior, while it is reduced to almost zero with the treatment of CFS II on OBM surface. Electrical stability test results show that the demulsification voltages of OBM and CFS II mixture fluids decreased as the percentage of the chemical preflush increased. CFS II will cause demulsification of OBM, reducing the demulsification voltage of the mixture and thus facilitating its removal. The viscosity measurement results demonstrate high compatibility of CFS I with OBM at different volume ratio combinations, which shows its pumpability is safe in field application. The shear bonding strength test indicates that the bonding strength increased by more than 3,212.8% with the use of CFS. Also tight cementation formed at the casing cement sheath interface (CCI), cement sheath formation interface (CFI), and no microannulus appearance. A case history of its use in a shale gas well in the field demonstrates the successful application of CFS to prevent sustained casing pressure (SCP) and maintain the sealing integrity of cement sheath.

An experimental study on examining the outcome of including surfactant to cement spacer design on mud removal efficiency and bonding of cement with formation

Effective spacer design is a key factor in cement's ability to produce a strong bond between the cement-casing and the cement-formation. Mud displacement, mud cake removal, and cement contamination with drilling mud are the different applications of the spacer. Furthermore applications include changing the wettability of the formation and casing, particularly when drilling is carried out with oil-based mud and the production zone is expected to be oil-wet. Oil wet formations can limit cement bonding with the formation, resulting in pressure transmission between hydraulic fracture stages and lack of zonal isolation.This paper investigates how adding surfactants to cement spacer design affects cement bond performance under reservoir temperatures, where the surfactants will help to mitigate the impact of oil base mud on cement performance, reduce drilling mud compatibility issues, change formation – casing wettability from oil-wet to water-wet, and reduce interfacial tension (IFT) between the mud and the cement.The investigation was conducted using Wolfcamp core samples. To simulate the oil well, the core samples were chopped into small pieces and aged in oil-based mud (8.8 ppg and 12.5 ppg) at reservoir temperature for 10 days. The wettability of the chip was then determined using the captive bubble method. The chips were then submerged in a spacer mixture. The experiment was carried out using three different surfactants (Anionic, Nonionic, and Zwitterionic surfactant). The wettability of the chips was tested again after they were exposed to the aforementioned spacers to see how surfactants affected the wettability. The interfacial tension (IFT) between the spacer and the crude oil was also measured. To investigate the mixability issue caused by the presence of surfactants in the spacer design, oil-based mud and spacer compatibility tests were done. In addition, beaker and rotor cleaning experiments were used to assess the efficacy of various surfactants in removing mud.

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.

Evaluation and suitability of a biomaterial as oil-based drilling fluids viscosifier using chemical structural properties approach

Mucuna solannie is a locally sourced material in Nigeria and other parts of Africa that enhances the viscosity of a drilling fluid. Due to its effectiveness, studies have been carried out on the structural properties of its seed flour for suitability as additive in oil-base mud. The chemical structures, name and other physiochemical properties of Mucuna solannie were determined using X-Ray Diffraction method, and the Fourier Transform Infrared Spectrometer. The scanned sample of Mucuna solannie was used to confirm the molecular bonding form, chemical structures and certain functional groups as basis of spectrum type. The result showed that Mucuna solannie was close to chitosan with covalent bonded molecular structure having calcium salt alone. It is a crystalline polymer and would require high calorific value to break the bonding energy existing in the molecules. Then, the FTIR discovered some functional groups and the position of carbon-carbon, carbon-hydrogen indicating the double bond. Â

Insights into the deoiling efficiency of oil-based cuttings by surfactant-free microemulsions

Oil-based cuttings (OBCs) produced during shale gas exploration are classified as hazardous waste, and are difficult and expensive to dispose of. Appropriate disposal of such OBCs has become a key issue requiring urgent attention. Here, we have applied surfactant-free microemulsions (SFMEs) to deoil OBCs. The deoiled OBCs, the recovered SFMEs, and the base oil have been characterized. Studies have shown that gentle stirring and mixing of n-hexane/tert-butanol/water (30:65:5 wt%) can form a cleaning agent that serves as an SFME. The oil content of the OBCs after deoiling by SFMEs was less than 1%, and the remaining solid phase showed no hazardous characteristics. The optimum conditions for cleaning OBCs with the SFME have been identified as 30–35 °C, a duration of 20 min, a solid–liquid mass/volume ratio of 1:4, and a stirring speed of 200 rpm. Thereafter, samples are optimally dried at 100 °C for 50 min. The recovered cleaning agent can be reused efficiently. The recovered base oil was essentially unchanged, except for some contamination with organic additives from the oil-based mud. The deoiling mechanism of OBCs with an SFME mainly depends on the strong solubilization ability of the SFME.

Development of a New Technique for Emulsifiers Optimization

Summary The primary and secondary emulsifiers of the oil-based muds (OBMs), which are the main expensive chemicals, need to be added to control the emulsion stability and the mud properties. Invasion of the filtrate introduces excess emulsifiers in the reservoir and leads to formation damage in forms of wettability alteration and permeability reduction, hence resulting in a decrease of the well productivity. This is recognized as one of the major mechanisms of the formation damage during overbalanced drilling, having significant economic impact on the petroleum industry, particularly for high-pressure and high-temperature wells. In the present work, experimental study has been carried out to assess the performance and the influence of the emulsifier’s concentration on the emulsion stability and the formation damage. A new technique has been developed based on the particle size analyzer (PSA), which can be used for optimizing emulsifier’s concentration and assessing the quality performance of various emulsifiers. The optimization and the emulsion stability results have been validated by standard American Petroleum Institute (API) testing procedure and return permeability tests. The key parameters which are useful and relevant to optimum emulsifier’s selection are to prevent the barite sag and to minimize the formation damage to increase the well productivity.

The effect of oil extraction on porosity and methane adsorption for dry and moisture-equilibrated shales

The porosity and methane adsorption capacity of shale used to estimate gas in place (GIP) are affected both by moisture and oil residing in the pore structure, as well as oil naturally present from maturation, which can include contaminant drilling mud fluids used for drilling. To demonstrate the impact of extractable oil on methane adsorption capacity for both dry and moisture-equilibrated shales, two overmature shales from China (SH1, SH2) and two lower mature shales from UK (BS3, GH4) have been investigated. The oils extracted from the overmature shales (<0.5 wt% TOC) are in low yield and arise from oil-based drilling mud, while the much higher yields from the lower maturity UK shales (1.1–2.5 wt% TOC) is mainly from oil generated by maturation. After extraction, minimal changes (<5%) in total nanopore volume (<100 nm) were observed for the dry over mature shales, but significant increases (95 and 176%) were observed for the dry lower maturity shales. More than 60% of the extracted oil resides in micro and mesopores, and removal could unblock the micropore necks and enlarge the accessible meso and macropore volume. Moisture contents are lower for extracted shales, with reductions of 7–37% observed. Methane equilibrium adsorption capacities increased after oil extraction for both the dry and wet shales, especially for lower maturity shales, where increases were over 200% for the wet shales. Henry’s Law was used to show that there were not significant amounts of dissolved methane in oils for the dry shales. Extracting oil from shales prior to determining the porosity and methane adsorption capacity can lead to the GIP being over-estimated for moisture equilibrated shales, particularly for oil-window shales where an overestimation of 22% was obtained for the shale investigated in this study. These findings provide a better understanding of the combined impacts of residual oil and water on GIP and avoid its overestimation.

Eco-friendly bioremediation approach for crude oil-polluted soils using a novel and biostimulated Enterobacter hormaechei ODB H32 strain

Petroleum oil contaminants have become severe ecological problems and negatively impact human health. It is, therefore, imperative to identify environmentally friendly approaches to remediate oil-polluted environments. Therefore, bacterial oil degradation stimulated with a nitrogen source under optimum conditions was assessed in this study. Based on the 16S rRNA analysis, strain ODB H32 recovered from oil-based mud of some petroleum drilling sites in the western desert, Egypt, was identified as Enterobacter hormaechei. The metabolic fingerprint of E. hormaechei, achieved using BIOLOG GEN III, revealed that the strain could utilize diverse carbon and chemical sources. Also, E. hormaechei could biodegrade 0.6% of oil under optimized pH (7.0) and temperature (30 °C) conditions. Analyzing different nitrogen stimulants revealed that peptone ˃ yeast extract ˃ ammonium nitrate ˃ urea enhanced the growth of E. hormaechei on mineral salts medium (MSM). Analysis by capillary gas chromatography revealed maximum (70.7%) degradation of peptone by E. hormaechei, indicating that peptone was a good biostimulant for oil degradation. These findings recommend using biostimulated E. hormaechei as an eco-friendly approach for remediating oil-polluted environments, under optimized conditions, especially in arid regions like the western desert of Egypt.

Experimental Evaluation of Locally Synthesized Biodiesel Drilling Fluid

Diesel oil has been the preferred base fluid for the formulation of oil-based drilling mud. Diesel oil has negative effects on the environment and there is a growing need for more environmentally sustainable alternatives that can be technically compared to diesel base oil. In recent times, the use of vegetable oils as drilling fluid base oil has been of interest. In this study, 1378 kg/m3 of palm kernel oil-based mud (PKOBM) and palm kernel oil biodiesel based mud (BDBM) were experimentally formulated. BDBM was synthesized by the transesterification of vegetable (palm kernel) oil. The performance of PKOBM and BDBM was then evaluated against conventional diesel oil-based mud (DOBM). The evaluation performed was based on the rheological, filtration and wall building properties, emulsion and thermal stabilities, and acute toxicity of the formulated drilling fluid systems. The results obtained from the study reveal that the mud systems (PKOBM and BDBM) show a typical Herschel-Bulkley (modified power-law) drilling mud rheological pattern at temperatures of 49°C, 66°C and 80°C. BDBM showed comparable rheological properties with better hole cleaning capacity as indicated by a lower flow index. For the filtrate loss test, BDBM exhibited a slightly lower filtrate loss compared to DOBM, whereas PKOBM had a higher fluid loss of 4.4 ml. For the filter cake and thermal stability test, there were no significant changes between DOBM and BDBM, whereas PKOBM had the least desirable performance. BDBM exhibited the most stable emulsion of 1274 volts breaking voltage and PKOBM, the least with 739 volts compared to 1169 volts breaking voltage of DOBM. This study concludes that BDBM could be used as an environmentally sustainable substitute for diesel oil-based mud (DOBM).

Nonlinearity in large amplitude oscillatory shear of drilling fluid: A comparative study on the oil and water base muds behavior

A viscoelastic material exhibits both fluid (viscous) and solid (elastic) like properties simultaneously. The rheological behavior of drilling fluids is customarily measured under the assumption of pure viscous flow, yet they exhibit both viscous and elastic characteristics when subjected to deformation. Some imperative properties of drilling fluids such as gel strength, yield stress, and sag tendency at near-zero shear rate region are categorically under the influence of viscoelastic behavior and have not yet been completely understood due to the lack of appropriate measurement methods. Characterizing the complete rheological profile of material requires measuring linear and nonlinear viscoelastic responses at a wide range of stress/strain levels. The viscoelastic nonlinearity can be characterized under Large Amplitude Oscillatory Shear (LAOS) tests. This study presents a large amplitude oscillatory shear rheology investigation of two water-base (Lignosulfonate and KCl/polymer) and two oil-base (low and high temperature) drilling fluids each in three states; unweighted, weighted, and weighted-contaminated. The viscoelastic nonlinearities of four fluid samples were investigated experimentally as a function of strain amplitude and strain-rate space at different temperatures. The results were described using Lissajous-Bowditch (L-B) plots and local nonlinear viscoelastic dynamic moduli through an oscillatory shear cycle. Structural stability of fluid samples was also studied using the creep-recovery test. The nonlinear viscoelastic behavior of drilling fluids was comprehensively compared and distinguished to understand their nonlinear shear mechanism. As a result of the creep-recovery test at 150 °C, high-temperature oil base mud provided higher thermo-structural stability and zero shear viscosity than those of Lignosulfonate, KCl/polymer, and low-temperature oil-base muds. While the elastic nonlinearity was found to be strain/strain rate softening, the nonlinear viscous character was recorded as shear/shear rate thinning at large strain rates for all drilling fluid systems. Quite a different shear mechanism was detected at low and moderate strain rates. Shear rate thinning was found to be the dominant mechanism for all fluids except Lignosulfonate mud samples that demonstrated shear-thickening behavior at moderate strain rates at 25 °C. At high temperatures (100 °C and 150 °C), shear rate thickening followed by shear rate thinning behavior was governing mechanism under the low and moderate strain rates in all mud samples except KCl/polymer muds. An inverse behavior (shear rate thinning followed by shear rate thickening) was observed through low and moderate strain rates in KCl/polymer muds at 100 °C and 150 °C. Therefore, as revealed from the LAOS test results, shear rate thickening behavior at low to moderate strain rates is in contradiction of the commonly known shear thinning behavior for a drilling fluid undergoing viscous deformation. This finding explains the facts underlying some important properties of drilling fluids such as gel structure formation, hole cleaning ability, and sag tendency.

Modelling of the cooling effect enhancement in drilling fluid using nanotechnology

Drilling fluid is indispensable to assure the safety and success of a drilling operation. Besides the normal drilling fluid such as water-based mud or oil-based mud, a new kind of drilling fluid has emerged recently, which consisted of the use of nanotechnology. The aim of this paper is to study the cooling effect of nano-drilling fluid used in the petroleum industry. A dynamic model that included a reservoir formation, a well, and a drill string in the drilling process with drilling fluid circulation was built for this objective. Navier-Stoke equation was used for the fluid flow inside the well and the drill string, while Darcy’s equation was used for the flow inside the formation. The rise of temperature due to friction was also accounted for in this model. Two types of drilling fluid were used in the simulation: the normal drilling fluid and the one using nanotechnology. The change of temperature in the wellbore and in the formation over time with these two types of drilling fluid was observed at various positions: at the bottom hole where the drilling bit is constantly in contact with the formation, and at other places further away from the bottom hole. The simulated results showed that, although the temperature fluctuated in the two cases but on average, the nano drilling fluid gave a better cooling effect in comparison with the normal one. This article is the first study about the application of nanoparticles in drilling fluid in Vietnam using an integrated modeling method. The approach proposed in this article can be applied efficiently in practical applications of nano drilling fluid for petroleum drilling in Vietnam. However, it is noted that this research treated typically the technical side of the application of nanotechnology in drilling fluid, while it will be necessary to asset the financial aspect in order to make this technology a real-life application.

The Research of Oil Washing Method for Oil-Based Mud Cuttings Samples from Deep Water Oil and Gas Exploration Wells

The Research of Oil Washing Method for Oil-Based Mud Cuttings Samples from Deep Water Oil and Gas Exploration Wells

Influence of Cyclone Oil Desorption Technology on the Change of Oil-Based Mud Cuttings Properties

Influence of Cyclone Oil Desorption Technology on the Change of Oil-Based Mud Cuttings Properties

Attenuation of Heavy Metals from Waste Oil-Based Drilling Mud using Locally Produced Coconut Shell-Based Activated Carbon

Most toxic Heavy Metals (HM) persist in oil-based mud and ecosystem for many decades after the application of mud for drilling oil and gas wells. This study assessed the attenuation of such heavy metals from waste oil-based mud using activated carbon produced locally. The oil-based mud analysed presented variable levels of Iron (Fe), Copper (Cu), Nickel (Ni), Potassium (K), Arsenic (As), Chromium (Cr), Manganese (Mn) and Zinc (Zn). Adsorption is a highly effective means of separation to remove a wide range of pollutants in waste streams. Coconut shell activated carbon (CS-AC) was locally produced to remove heavy metals from the waste oil-based mud to encourage value addition to waste. The adsorption data was fitted to Langmuir and Freundlich isotherm model using linear regression analysis. The data was more fitted to the Langmuir isotherm as indicated by the high goodness of fit values (R2). To reduce the heavy metal concentrations below threshold levels optimum CS-AC dosage required for Fe, Cu, Ni, K, As, Cr, Mn and Zn is 5 g/l of CS-AC for a contact time of 30 minutes. The characterization of the produced carbons shows good results comparable to other commercial activated carbons. CS-AC is a viable and economical product for the removal of toxic heavy metals from waste oil-based mud before disposal.

The Use of Crude Coconut Oil (CCO) as an Alternative Oil Base Mud (OBM) for Drilling Operations by "VICOIL" Standard Drilling Simulation Rig

Shale is one of the rocks that often causes drilling problems because shale tends to swell or swell when in contact with mud filtrate, mainly water-based or Water-base Mud (WBM). This study aims to determine how the performance of Oil-base Mud (OBM) based on Crude Coconut Oil (CCO) in overcoming the swelling problem. The methodology used consists of drilling simulation and cutting analysis in the X-Ray Diffraction (XRD) laboratory. The series of activities in the study began with the preparation of rock layers, followed by testing the penetration rate using Water-base Mud as a comparison. After cutting analysis was carried out in the XRD laboratory of UPN "Veteran" Yogyakarta with the Rigaku tool, then replaced the type of drilling fluid Oil-base Mud with basic materials alternative to Crude Coconut Oil (CCO) and followed by a penetration test. Rate of Penetration (ROP) test results from WBM with Rheology 1 at interval depth of 1.64 ft-3.28 ft is 442.8 ft/h, Rheology 2 at interval depth of 4.92-6.5 ft is 118.5 ft/hr on the first day. Swelling occurred and results in pipe sticking at depth of 3.28 and 6.5 ft. Based on the Bulk Mineral analysis, clay mineral content is 23.84%. Based on the Clay Oriented, smectite dominates the clay by 29.09%. Based on MBT, shale belongs to class B (illite and mixed-layer montmorillonite illite), where this mineral can expand. Based on a Geonor As test, 5.18% of the cutting can develop when exposed to water. The drilling fluid was replaced with Oil-base Mud based on alternative Crude Coconut Oil (CCO), and obtained ROP Rheology 1 at Interval depth of 3.28 ft-4.92 ft is 492 ft/h and Rheology 2 at Interval depth of 6.5 ft-10.5 ft is 480 ft/h. The results of the Compressive Strength test interval A on the first, third, and fifth days were 31,699 psi, 42,265 psi, and 52,831 psi. The results of the Compressive Strength test interval B on the first, second, and third days were 31,496 psi, 41,517 psi, and 52,971 psi. Based on clay mineral analysis and magnitude of ROP value, is known that Crude Coconut Oil (CCO) based Oil-base Mud is effective because during the simulation, there are no drilling problems, and the resulting ROP value is greater than the first day Water-base Mud.

Optimization and Process Modeling of Viscosity of Oil Based Drilling Muds

The viscosity of oil-based drilling mud was optimized and modeled in this study. Imported bentonite and local clay additives, and diesel oil (base fluid) were used to prepare two muds; oil-based mud with bentonite (OBMB) and oil-based mud with clay (OBMC). The local clay was beneficiated with hydrochloric acid (HCl) and then characterized using an x-ray fluorescence (XRF) spectrometer. The result of the characterization revealed that the local clay is more silica (SiO2) than kaolin. The interactive effects of three operating conditions, temperature, aging time, and bentonite/clay dosage, respectively, on the viscosity of each mud were determined. The Response surface methodology (RSM) of the central composite design tool of Design Expert software (version 12) was employed to optimize the viscosity of each mud. The RSM carried out revealed the interaction between the three operating variables of temperature, time, and dosage of bentonite/clay and their impact on the viscosity of each mud. Optimum viscosity of 19.3 cP for OBMB and 25.9 for OBMC were obtained at temperature of 313K, aging time of 30 minutes and bentonite/clay dosage of 9 wt%. Analysis of variants (ANOVA), mathematical modeling, and graphical plots further established the actual interaction between the response-viscosity of each mud and the considered process factors. The generated models revealed linear, interactive, and quadratic equations which adequately described the relationship between the viscosity of each mud and the considered factors of temperature, time, and dosage. The experimental data and the predicted results were compared, and the model predicted values are in good agreement with the experimental results. Doi: 10.28991/HEF-2021-02-04-09 Full Text: PDF