Mud Cakes Research Articles

Development of a high temperature resistant nano-plugging agent and the plugging performance of multi-scale micropores

Nano-plugging agents (NPAs) are very important to stabilize the wellbore by reducing pressure transmission and drilling fluid invasion during drilling engineering. A functionalized polystyrene latex (FPL) was synthesized by micellar polymerization as a NPA for drilling fluids. The particle size and thermal stability of FPL were characterized by particle size analysis and thermogravimetric analysis (TGA). The experimental results showed that the initial thermal decomposition temperature of FPL was 310.6 ℃. The medium value of particle size distribution (D50) of FPL decreased from to 371–235 nm after aging at 220 ℃, indicating that FPL had good temperature resistance property. The plugging method and plugging performance of FPL for four filter media with pore sizes from 0.01 µm to 10 µm were introduced. FPL itself was difficult to plug the filter papers and ceramic filter disks, but FPL could reduce fluid loss of bentonite suspensions. SEM observation indicates that FPL could improve the quality of mud cakes and plug the small pores of ceramic filter disks. For microporous membranes and artificial mud cakes with low permeability, FPL aqueous suspensions had a good plugging performance. The plugging experimental results conformed well to the 2/3 bridging rule. This paper provides a good reference for the development of high temperature NPAs and the establishment of evaluation methods of NPAs.

Application of Cellulosic Fibrous Material from Agro Waste as Filtrate Loss Modifier in Aqueous Mud-Morphology at HTHP Conditions

Controlling the filtration characteristics of any drilling fluid does not only include the control of the filtrate volume penetrating into the formation; but also the ability of the mud to deposit a thin low-permeability filter cake on the wall of the wellbore quickly. The permeability of the filter cake is very dependent on the particle size because when small size particles are used, the permeability decreases, because of the fact that colloidal particles get packed very tightly. This study investigated the filtration and filter cake characteristics of water-based mud (WBM) using fibrous cellulose from Tiger Nut waste and the guar gum. American Petroleum Institute (API) Recommended Practice Standard Procedure for Field Testing Drilling Fluids, API RP 13B-1 was applied during the analysis. Statistical analysis of the experimental data was conducted and the R2 value (0.99) showed that the experimental method adopted was replicable. Mud samples B2 and C2 gave an optimum result and their mud cakes developed under High-Temperature High-Pressure (HTHP) condition were dried and further analyzed with scanning electron microscope (SEM). The results showed that the filter cakes SEM structure for cellulosic fibrous from agro waste and guar gum exhibits similar characteristics; and the mud cakes was firm after soaking with 15% HCl for thirty minutes but started dissolving after one hour. The SEM analysis inferred that the filter cake morphology shows a good particle-pore interlocking for sample C2 than B2.

Pengaruh Perbandingan Terigu Dengan Tepung Kecambah Kacang Merah (Phaseolus vulgaris L.) Terhadap Karakteristik Kue Lumpur


 
 
 The purpose of this study was to determine the effect of wheat flour comparison with red bean sprout flour on the characteristics of lumpur cakes and to determine the ratio of wheat flour to red bean sprouts flour which can produce mud cakes with the best characteristics.This research used a Completely Randomized Design (CRD) with a comparison of flour and red bean sprouts as treatment. Treatment consisting of 6 levels (100%: 0%, 80%: 20%, 60%: 40%, 40%: 60%, 20%: 80%, and 0%: 100%). The experimentation was repeated 3 times So that it is obtain 18 experimental units. Observed variables of moisture content, ash content, protein content, fat content, crude fiber content, color, aroma, taste, texture, and overall acceptance of lumpur cakes. The data obtained were then analyzed by variants and if there was any effect on the treatment, then continued with Duncan test. The results showed that the addition of red bean sprout affected moisture content, ash content, protein content, fat content, crude fiber content, color, aroma, taste, texture, and overall acceptance of lumpur cakes. The best characteristic of lumpur cake substitution was 60% wheat flour and 40% red bean sprouts flour that produced moisture content of 35,62%, an ash content of 0,78%, protein content of 11,09%, a fat content of 36,67%, crude fiber content of 16,47%, regular color (normal), aroma (like), soft texture (like), taste (like), and overall acceptance (like).
 
 

Effective Modified Xanthan Gum Fluid Loss Agent for High-Temperature Water-Based Drilling Fluid and the Filtration Control Mechanism.

Xanthan gum (XG) was widely used as an oilfield chemical treatment agent because of its environmental protection and diverse functions. With the increased drilling depth and formation complexity, the shortcomings such as poor solubility and low resistance to temperature were gradually exposed. In this study, a modified XG derivative XG-g-AAA was synthesized by grafting XG with acrylic acid (AA), acrylamide (AM), and 2-acrylamido-2-methylpropane sulfonic acid (AMPS). The chemical structure of XG-g-AAA was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance (1H NMR). Then, the solubility, high-temperature rheology and filtration properties, resistance to Na+/Ca2+, and compatibility were investigated. Results show that (1) both in aqueous and salt solutions, XG-g-AAA can completely be dissolved within 15 min. The significant improvement of the solubility of XG-g-AAA makes it more suitable for field use. (2) XG-g-AAA is less sensitive to high temperatures, and the viscosity decay decreased by 23.3 and 21.3% than XG at 150 and 180 °C, respectively. XG-g-AAA-based drilling fluid is a high-quality drilling fluid with significant shear thinning behavior, and the power-law model is the optimal model to describe its high-temperature rheology. Within 150 °C, 1.5% XG-g-AAA can maintain a reasonable value of the flow behavior index (n) (0.55–0.69), filtration volume (<11.6 mL), and sufficient gel strength (GS). At 150–200 °C, 3% XG-g-AAA is recommended. The value of n was in the range of 0.45–0.62, and the fluid loss was within 10 mL. However, 3% XG-g-AAA cannot provide enough GS at 200 °C; thus, a shear strength-improving agent is recommended to be added. (3) XG-g-AAA showed excellent contamination tolerance and compatibility. It could resist 2 wt % CaCl2 and 35 wt % NaCl at room temperature and 0.75% CaCl2 and 5% NaCl after 150 °C aging. (4) XG-g-AAA showed compatibility with sulfonated drilling fluids and could replace commercial fluid loss agents in the formula. Furthermore, the high-temperature fluid loss control mechanism was discussed by analyzing the effects of XG-g-AAA on the bentonite layer spacing, particle size distribution, stability of the colloidal system, and mud cakes.

Experimental Research on the Impact of Interface Temperature on the Adhesion Properties of Clay under the Condition of Different Contacting Time

Mud cakes are very likely to occur at the shield cutter when the shield machine passes through a clay stratum, which adhere to the cutter and reduce the excavation efficiency. Due to the thrust of the cutter, the mud cakes are compacted and cause friction at the soil-structure interface, which results in high temperature and aggravates the adhesion, and the effect tends to become stronger as the heating process lasts. In this paper, the effects of the interface temperature and the contacting time between the soil and the hot surface on the adhesion properties of the soil were studied by a self-made adhesion test device. According to the findings, at low interfacial temperature (≤40°C), both the adhesion force and the amount of adhered soil were insignificant in a short term, and the effects were found to be strengthened as the contacting time went on; at the high interfacial temperature (≥50°C), very significant soil adhesion occurred at the structure surface within a short time, and as the contacting time increased, the amount of the adhered soil decreased rapidly while the adhesion force kept increasing, and both tended to remain a constant and become independent with the temperature after a long-term contact. This study is of guiding significance for understanding the formation and development of the shield mud cakes during shield construction.

Experimental Research on the Adhesion Characteristics of Clay to Structures with Different Materials

When the shield machine passes through the clay layer, the clay debris cut by the cutter head usually adheres to the surface of the cutter head and is easy to form mud cakes after extrusion, which affects the safety and efficiency of construction. For the structure made of different materials, due to the different surface properties, the adhesion characteristics of clay are also different. So, selecting proper materials for the soil contacting parts in the shield machine can effectively reduce the adhesion between the structure and soil, decrease the clay adhering to the surface of the shield cutter, and reduce the possibility of further productions of mud cake. Therefore, studying the adhesion properties of clay to different materials and understanding the adhesion rule of clay to soil contacting structures are of guiding significance when selecting the materials of soil contacting parts. In this paper, the adhesion properties of cohesive soil to commonly used construction materials were studied by a self-made adhesion test device, including steel, iron, copper, aluminum, and engineering plastics (polyamide). According to the findings, the separation process of adhesion between soil and the structure by an external force can be divided into four stages, which are the adhesive elastic development stage, adhesive plastic development stage, failure stage, and detachment stage. The adhesion forces and the amount of soil adhered to the structures made of the selected materials are found to vary from each other. The adhesion forces ranked from high to low are, respectively, found on the iron, plastic, aluminum, steel, and copper surfaces. The material with the most amount of adherent soil is aluminum, followed by iron, steel, copper, and plastic.

Effects of anti-clay agents on bubble size distribution and stability of aqueous foam under pressure for earth pressure balance shield tunneling

The earth pressure balance (EPB) shield inevitably encounters heavy clay soils during tunneling, which form mud cakes on the cutter head. To prevent this, it is necessary to add anti-clay agents to foam agents. However, the effect of anti-clay agents on foam properties and its optimal concentration under different conditions remain unknown. In this study, the bubble size distribution and half-life of foam produced by foam agents and anti-clay agents under pressure were measured and analyzed. The results show that the mean bubble radius decreases with the addition of anti-clay agents at 0 bar but increases at a pressure of 1 bar or 2 bar. The anti-clay agents weaken the stability of foam, and optimal concentrations of anti-clay agents for different test pressures are proposed. The test results obtained provided guidance for selection of the optimal concentration of anti-clay agents to be used in EPB shield tunneling.

Characteristics of Hydration Damage and Its Influence on Permeability of Lamellar Shale Oil Reservoirs in Ordos Basin

The continental shale oil reservoir has low permeability, high clay content, rich lamellar structure, and strong heterogeneity, which makes the reservoir vulnerable to hydration damage. In order to study characteristics of hydration damage and its influence on permeability of lamellar shale oil reservoirs, a series of experiments such as high-pressure mercury injection, steady gas permeability, rock thin section identification, and scanning electron microscope were carried out with the downhole core in Ordos Basin as the experimental object. The effects of water and water-based drilling fluid on pore size distribution, permeability, and rock microstructure were analyzed. Results show that the pore size of the reservoir is mainly nanoscale, and the pore size of shale changes most dramatically in the stage of hydration for 12-24 hours, while that of tuff changes most dramatically in 24-48 hours. The permeability increases rapidly with hydration time and then tends to be stable, among which the permeability of samples with lamellar structure in the direction parallel to the lamellar structure is most easily affected by hydration and changes fastest. Hydration leads to the formation of new pores, new fractures, and the expansion of existing fractures in rocks, especially in the strata containing large amounts of terrigenous clastic, lamellar structure, and pyrite. The new seepage channel increases the permeability of rock, and the soil powder and plugging particles in drilling fluid are easy to form protective mud cake in these places. These protective mud cakes not only change the microstructure of rock but also inhibit the influence of hydration on the pore space and permeability of rock, which play an effective role in preventing the mineral shedding on the rock surface, reducing the increase of micropores and delaying hydration.

Dispersant for Reducing Mud Cakes of Slurry Shield Tunnel Boring Machine in Sticky Ground

When a slurry shield tunnel boring machine (TBM) encounters sticky ground during tunneling, mud cakes often occur on the cutter head due to the high stickiness of soil. The mud cakes caused several negative issues, such as high torque demand, advancement rate reduction, and additional costs. Existing studies have largely focused on Earth pressure balance TBMs; research on formation and mitigation measures of mud cakes in slurry shield TBMs is limited. Therefore, this study proposes the addition of dispersant to the slurry to prevent mud cakes during the tunneling of slurry shield TBMs by reducing stickiness of excavated clay. The basic properties of slurry were measured experimentally, and the effectiveness of dispersant in reducing the potential for mud cakes was investigated through mixing tests and viscosity experiments. A statistical analysis of the data was performed to determine relationships between slurry properties and material behaviors. The results showed that the slurry with dispersant had a lower viscosity and formed filter cakes more quickly, thereby meeting the performance requirements of a supporting fluid for slurry shield TBMs. Further, dispersant effectively reduced the empirical stickiness ratio and suspension viscosity. Therefore, a slurry with an appropriate dispersant content could effectively reduce the potential for mud cake formation.

A new eco-friendly and low cost additive in water based drilling fluids

This study investigates the possibility of using rice husk ash as an additive to develop an environmentally friendly and low-cost drilling fluid system. The rice husk ash was added as an additive to water-based bentonite drilling fluids at different concentrations ranging from 2 wt% to 15 wt%. Rheological and filtration properties of each drilling fluid developed were measured by using a viscometer and standard low-pressure low-temperature filter press. Subsequently, cutting carrying index, minimum annulus velocity required to clean bottom of the well efficiently, flow behaviour index and permeability of mud cakes of the formulated systems were calculated in order to assess performance of the systems. The results demonstrated that the rheological and properties were improved depending on concentration of rice husk ash introduced. With the introduction of 15 wt% concentration of rice husk ash, while apparent viscosity and yield point increased by 60% and 183%, respectively, thixotropy and plastic viscosity decreased by 29% and 63%, respectively. On the other hand, drilling fluid with 4% wt% content of rice husk ash reduced the fluid loss by 10%. Moreover, results showed that cutting carrying index, minimum annulus velocity required to clean bottom of the well efficiently and flow behaviour index of the enhanced with the exploitation of rice husk ash in the drilling fluid. This study showed that rice husk ash as a promising additive to use in the water-based bentonite drilling fluids when properly implemented, and hence reducing the impact on the environment, and the total cost for drilling.

Experimental Research on the Impact of Temperature on the Adhesion Characteristics of Soil-Structure Interface

Under the working condition of mud cake, the continuous action between the shield cutter head and the soil on the excavation surface can generate high temperature in the process of shield tunneling and excavation, which changes the characteristic of the adhesion between the soil and the cutter head to intensify the phenomenon of making a mud cake on cutter, finally leading to a vicious circle. To study the effect of temperature on the characteristics of the adhesion of the soil on the surface of the structure, the soil adhesive situation and adhesion force at different interface temperatures were tested through a self-made experiment device. According to the result, it was indicated that the moisture content has a significant effect on the adhesion force of the soil, and the adhesion force firstly increased and then decreased with the increased of the moisture content and reached the maximum value near the plastic limit moisture content. The adhesion force changes very gently when the interface temperature is low. When the temperature reached 50°C, the adhesion force continues to increase as the interface temperature continuously increases except for the soils with high moisture content; moreover, the interface temperature has a great influence on the content of soil adhered on the structure surface. As for the soil with moderate moisture content ( ω = 21.21 ~ 31 %), this content of the adhered soil increased exponentially with the increase of interface temperature; this content firstly decreased and then increased when the moisture content was high. When the soil was dry, there was almost no adhered soil on the surface and the interface temperature had no effect on the adhesive situation. By comparing and analyzing the adhesion state of the soil on the surface of the structure, the influence of temperature on the adhesion characteristics is mainly reflected on the variation of the soil moisture content within the influence range of the interface, the variation of the energy required for the destruction of the adhesion interface, and the change of the location of the weakest antistripping plane induced by both before. This research can better understand the law of formation and development of mud cakes and provided a new idea of solving the problem of mud cakes on the cutter head.

Influence of tailor-made TiO2/API bentonite nanocomposite on drilling mud performance: Towards enhanced drilling operations

A novel tailor-made TiO2 nanoparticles-bentonite (TNBT) nanocomposite-enhanced drilling mud was tested. The drilling mud showed excellent performance; (i) lubricity was enhanced, (ii) thin and well-intact mud cakes were created, (iii) coating was provided on shale and bentonite plugs, and (iv) clay and shale swelling were mitigated, hence these features ensured a platform for sustainable oil and gas well drilling. The synthesised TNBT nanocomposite followed the one-third bridging rule, i.e., these nanoparticles can bridge nanopore throats in shale pellets and American Petroleum Institute (API) standard bentonite pellets. The tailor-made TNBT nanoparticles were characterized by X-ray diffraction, and scanning electron microscopy. The coefficient of friction and filtrate loss of TNBT-enhanced muds were determined with a lubricity tester, and an API filter press, respectively. Additionally, shale and clay swellings were determined with a linear swell meter. The coefficient of friction was reduced after 0.8 g of TNBT was added to 350 ml drilling mud, resulting in a 35% enhancement in mud lubricity. The new mud also drastically mitigated the swelling in shale and clay when compared to conventional mud. The swelling inhibition was attributed to an increase in the mud viscosity and improved nanopore plugging characteristics, which resulted in less water infiltration. Thus, drilling mud supplemented with the tailor-made TiO2 nanoparticles-bentonite nanocomposite showed superior characteristics and a good potential for field operations.

Evaluating the locally sourced materials as fluid loss control additives in water-based drilling fluid

In the exploration for hydrocarbons, a successful drilling operation to the desired depth hinges on the effective performance of the formulated drilling fluid. Apart from carrying drill cuttings to the surface, another major function of the fluid is to seal off the walls of the wellbore to prevent fluids from coming into and out of the wellbore while drilling a well. Numerous commercial fluid loss additives: carboxymethyl cellulose (CMC), polyanionic cellulose (PAC), among others have been in existence with their drawbacks and effect on the total drilling cost. This study evaluates the use of locally sourced materials: Detarium microcarpum, Brachystegia eurycoma and rice husk, as fluid loss control additive in the water-based drilling fluid. The materials were prepared, ground and sieved to 125 microns. Four sets of water-based drilling muds were formulated using the local materials and CMC as fluid loss control additives. The mud formulation was based on the American Petroleum Institute (API) standard of 25g bentonite to 350mL of water. Also, the filtration test of the formulated muds was performed using API recommended practice for static filtration test at low temperature - low pressure (LTLP) condition. The results obtained showed that Detarium microcarpum and rice husk fluid loss volume and filter cake thickness were comparable with that of CMC from additive content of 10g, while Brachystegia eurycoma was comparable from additive content of 15g. Furthermore, the composite additive results indicated that Detarium microcarpum-rice husk at 95% Detarium microcarpum-5% rice husk performed better than Brachystegia eurycoma-rice husk of the same combination. Additionally, the fluid loss volume and filter cake thickness of Detarium microcarpum-rice husk additive were comparable with CMC from 10g content. Also, the results revealed that the fluid loss volume and filter cake thickness obtained from the locally sourced materials were within API specification for fluid loss control agents. The mud filter cake characteristics exhibited by these materials depicted that they have slippery, smooth and soft mud cakes; thus, the characteristics of a good mud cake that will prevent differential pipe sticking.

An Investigation on the Function of Mud Cakes on the Inhibition of Low Molecular Inhibitor for Water-Based Drilling Fluids

The major low molecular inhibitors showed inhibition in the hydration of clay in the laboratory for water-based drilling fluids, according to the principle of intercalation adsorption. However, inhibitors have failed and caused serious engineering accidents in drilling oil and natural gas. This paper investigated the transmission of several of drilling fluids to indicate whether low molecular inhibitor for drilling can effectively inhibit the wellbore hydration. The inhibition of drilling fluid with the plugging of mud cakes, was significantly weakened based on the hydration expansion of cores and cutting recoveries. The residual contents of inhibitors were determined with the precolumn derivation of high-performance liquid chromatography (HPLC) analysis and were chartered with Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analysis in the structure of the derivative. The clogging behavior of the mud cake was described by environmental scanning electron microscopy (ESEM). Experiments show that 40 wt% to 90 wt% by weight of the corrosion inhibitor cannot pass through the mud cake in the dynamic filtration of the drilling fluid. The mud cake can be further divided into a nanostructure layer, a homogeneous layer and an anisotropic layer with different permeability. Most inhibitors should be limited to the nanostructure layer and the homogeneous layer.

Appraising the impacts of SiO2, ZnO and TiO2 nanoparticles on rheological properties and shale inhibition of water-based drilling muds

In recent decades, utilizing of water-based muds (WBMs) in drilling oil and gas wells is ever increasing comparing to oil-based muds and synthetic-based muds due to the lower environmental issues. However, the main drawbacks with WBMs are rheological properties inefficiency and shale swelling which have caused attentions turn to improvement of WBMs’ rheological properties. In this study, the effects of various nanoparticles (NPs) namely titanium dioxide (TiO2), silicon dioxide (SiO2), and zinc oxide (ZnO) on improving rheological properties and shale recovery rate of a WBM sample at two temperatures (25 and 50 °C) were investigated. The concentrations of NPs in the base mud were set at 0.01, 0.05, 0.1 and 0.5 wt%. The results revealed that by adding NPs, the plastic viscosity (PV) of base mud was noticeably increased at the both temperatures. The optimum concentration of all NPs for increasing PV was found to be 0.01 wt%. Furthermore, by increasing concentration of ZnO and SiO2 NPs up to 0.5 wt%, the base mud yield point value was considerably risen to around 13.3%, while by increasing concentration of TiO2 NPs, the mud yield point values were reduced to 23.5 and 20.2 (lb/100 ft2) at 25 and 50 °C, respectively. The optimum ZnO, TiO2, and SiO2 NPs concentrations for this purpose were found to be 0.05, 0.01, and 0.1 wt%, respectively. Moreover, ZnO and SiO2 NPs at concentrations below 0.05 wt% had the best performances for filtration loss control. The related reason is higher stability of these NPs in the aqueous phase and consequently, better mud cake pores filling act by them which caused the mud cakes permeabilities were noticeably reduced. Besides that, SiO2 NPs caused the highest 10 s and 10 min gel strength values and ZnO and TiO2 NPs in order had the lowest 10 s and 10 min gel strength values at all applied concentrations and temperatures. Finally, by increasing concentrations of all NPs, shale recovery rates have noticeably risen comparing to the base mud. SiO2, ZnO and TiO2 NPs in order were successful additives for shale recycling.

Rice husk and saw dust as filter loss control agents for water-based muds

When drilling with water based muds (WBM), significant fluid loss volumes from the mud into the formation can have adverse effects not just on the mud and its properties but also on the stability of the wellbore. Prevention of mud filter loss is one way of assessing the performance of a drilling mud. However, evaluation of the effectiveness or otherwise of a fluid loss control additive can be made by characterizing the mud cake formed. Interestingly, the mud cake characterization is one area that has been somewhat neglected in drilling fluid formulation with agro waste materials. Two cellulosic materials - rice husk and saw dust were chosen for the experimental study. The specie of the rice husk used was the African rice (Oryza glaberrima) while the dust from the saw milling of Oxystigma manni was utilized for this study. To ensure result acceptability, the rice husk and saw dust were ground and the resulting products were sieved to 1.25 × 10−4 m. The filtration characteristics of the formulated mud samples were tested using the American Petroleum Institute (API) filter press and in accordance to the API recommended practice for field testing WBMs. From the filter loss tests, it was observed that the ground rice husk prevented filter loss by an average of 77% compared to ground saw dust filtration control of 63%. In addition, it was observed that at higher concentrations, ground saw dust and rice husk prevented fluid loss to the minimum acceptable API standard. For the filter cake thickness measured in millimetres, ground rice husk exhibited thicker mud cakes when compared with the saw dust by an average amount of 14%. For the mud cake characteristics, the rice husk mud exhibited smooth and slippery cakes while the saw dust mud exhibited rough texture, sticky and firm cakes.

Thermoresponsive Bentonite for Water-Based Drilling Fluids.

As an important industrial material, bentonite has been widely applied in water-based drilling fluids to create mud cakes to protect boreholes. However, the common mud cake is porous, and it is difficult to reduce the filtration of a drilling fluid at high temperature. Therefore, this paper endowed bentonite with a thermo response via the insertion of N-isopropylacrylamide (NIPAM) monomers. The interaction between NIPAM monomers and bentonite was investigated via Fourier infrared spectroscopy (FTIR), isothermal adsorption, and X-ray diffraction (XRD) at various temperatures. The results demonstrate that chemical adsorption is involved in the adsorption process of NIPAM monomers on bentonite, and the adsorption of NIPAM monomers accords with the D–R model. With increasing temperature, more adsorption water was squeezed out of the composite when the temperature of the composite exceeded 70 °C. Based on the composite of NIPAM and bentonite, a mud cake was prepared using low-viscosity polyanionic cellulose (Lv-PAC) and initiator potassium peroxydisulfate (KPS). The change in the plugging of the mud cake was investigated via environmental scanning electron microscopy (ESEM), contact angle testing, filtration experiments, and linear expansion of the shale at various temperatures. In the plugging of the mud cake, a self-recovery behavior was observed with increasing temperature, and resistance was observed at 110 °C. The rheology of the drilling fluid was stable in the alterative temperature zone (70–110 °C). Based on the high resistance of the basic drilling fluid, a high-density drilling fluid (ρ = 2.0 g/cm3) was prepared with weighting materials with the objective of drilling high-temperature formations. By using a high-density drilling fluid, the hydration expansion of shale was reduced by half at 110 °C in comparison with common bentonite drilling fluid. In addition, the rheology of the high-density drilling fluid tended to be stable, and a self-recovery behavior was observed.

Effects of silica nanoparticles on the performance of water-based drilling fluids

In this research, two groups of experiments were conducted to investigate the effects of silica (SiO2) nanoparticles on the filtration and rheological properties of water-based drilling fluids. In the first group, bentonite, chrome-free lignosulfonate (CFL) and carboxymethyl cellulose (CMC) were used in different concentrations to obtain base fluids. Nanofluids were prepared by adding 0.5 g of four different silica nanoparticles into these drilling fluids. Comparison of rheological properties, fluid loss amounts and mud cake thicknesses were performed at two different temperatures (25 °C and 49 °C). It was concluded that all of the nanoparticles reduced the filtration efficiency of bentonite muds. On the contrary, a reduction in fluid loss was observed for some lignosulfonate muds containing nanoparticle. However, no significant change in mud cake thickness and rheological properties was seen for both drilling fluids.Since no positive effect was observed in the first part, further investigation was done with higher bentonite and nanoparticle concentrations than previous experiments. Moreover, only bentonite was used as additive to eliminate other parameters and to see more clearly the effect of nanoparticles in bentonite mud. Samples were formulated with 7% by weight of bentonite and 0.5% and 1.5% by weight of nanoparticles. It was seen that the amount of fluid loss is directly proportional to the nanoparticle concentration. Therefore, Darcy's Law was used to compare the permeability of mud cakes and it was confirmed that nanofluids form permeable mud cakes compared to base fluid.

The effect of lost circulation materials on differential sticking probability: Experimental study of prehydrated bentonite muds and Lignosulfonate muds

High mud loss is one of the major drilling problems that has caused severe problems throughout the oil well drilling history. One of the most common methods to reduce mud loss is using lost circulation materials (LCMs). Mud loss and LCMs change mud properties but the latter change that of mud cake as well. The main purpose of this research is to investigate the effect of mud loss and LCMs on mud cake thickness and differential sticking probability. Two mud types (prehydrated bentonite and lignosulfonate muds) are selected as the case studies. For prehydrated bentonite muds, the effect of cellophane and walnut shell additives are investigated. For lignosulfonate muds, the effect of sawdust and mica additives were investigated. Some similar mud compositions are chosen from reference papers in order to calibrate devices and compare the results. The API filter press is used for making mud cakes and testing mud loss. Mud cake characterization equipment is used for measuring the torsional resistance of the mud cake and examining the probability of differential sticking. It seems that the geometric shape of the additive is important in reducing filtrate loss and also reducing the probability of the differential sticking. In prehydrated bentonite muds, walnut shell and cellophane additives are the best reducers of the filtrate loss and the probability of the differential sticking, respectively. Also in lignosulfonate muds, mica and sawdust additives are the best reducers of the filtrate loss and the probability of the differential sticking, respectively.

A novel field applicable mud formula with enhanced fluid loss properties in High Pressure-High Temperature well condition containing pistachio shell powder

Sustainable technologies are the main concerns of the 21st century modified oilfield industries. The insufficiency of conventional drilling fluid formulations with a combination of hardly degradable hazardous chemicals as additives raise the demands of field-applicable innovative and environmentally friendly methods. Pistachio Shell discards as degradable wastes, which can intellectually apply in drilling fluid formulation. The experimental oilfield investigations of utilizing pistachio shell powder prove the significant enhancement of rheological properties, reduction of fluid loss and mud cake thickness in both API (Low Pressure —Low Temperature) and High Pressure—High Temperature (HPHT) conditions. The main point of concern is substituting polyanionic cellulose polymer, which frequently used in water-based conventional mud formulations with pistachio shell in the form of two distinct fine particle sizes. Both particle sizes prove their ultra practical properties to be used as fluid loss control agent. Also producing thin and high-quality mud cakes demonstrate their applicative field attribute. The relatively fine particle size (less than 75 μm) shows the maximum efficiency with %44 fluid loss reduction and the highest value of plastic viscosity, yield point, and gel strength, which are indicators of very appropriate rheology. Moreover, the cost analysis shows 13% reduction in the cost of preparing drilling fluid in compared to the fluid with polyanionic cellulose. The lab to field approach of the experiments increases the certainty of the field scaling practices and eliminates the demands of intermediate upscaling stages. The presented method successfully apply in one of the Iranian oil fields.