Oil-based Drilling Fluid System Research Articles

An Amphiphilic Multiblock Polymer as a High-Temperature Gelling Agent for Oil-Based Drilling Fluids and Its Mechanism of Action.

Oil-based drilling fluids are widely used in challenging wells such as those with large displacements, deepwater and ultra-deepwater wells, deep wells, and ultra-deep wells due to their excellent temperature resistance, inhibition properties, and lubrication. However, there is a challenging issue of rheological deterioration of drilling fluids under high-temperature conditions. In this study, a dual-amphiphilic segmented high-temperature-resistant gelling agent (HTR-GA) was synthesized using poly fatty acids and polyether amines as raw materials. Experimental results showed that the initial decomposition temperature of HTR-GA was 374 °C, indicating good thermal stability. After adding HTR-GA, the emulsion coalescence voltage increased for emulsions with different oil-to-water ratios. HTR-GA could construct a weak gel structure in oil-based drilling fluids, significantly enhancing the shear-thinning and thixotropic properties of oil-based drilling fluids under high-temperature conditions. Using HTR-GA as the core, a set of oil-based drilling fluid systems with good rheological properties, a density of 2.2 g/cm3, and temperature resistance up to 220 °C were constructed. After aging for 24 h at 220 °C, the dynamic shear force exceeded 10 Pa, and G' exceeded 7 Pa, while after aging for 96 h at 220 °C, the dynamic shear force exceeded 4 Pa, and G″ reached 7 Pa. The synthesized compound HTR-GA has been empirically validated to significantly augment the rheological properties of oil-based drilling fluids, particularly under high-temperature conditions, showcasing impressive thermal stability with a resistance threshold of up to 220 °C. This notable enhancement provides critical technical reinforcement for progressive exploration endeavors in deep and ultra-deep well formations, specifically employing oil-based drilling fluids.

Experimental Optimization of High-Temperature-Resistant and Low Oil—Water Ratio High-Density Oil-Based Drilling Fluid

Problems such as well loss and collapses in deep shale gas drilling are most often due to the development of cracks in the shale formation, resulting in significant leaks of drilling fluid, the sticking and burrowing of drilling tools, and other engineering accidents. In addition, the horizontal sections of wells are very long and issues of friction, rock transport, and formation contamination loom large. As a result, the performance of drilling fluids directly affects drilling efficiency, engineering accident rates, and reservoir protection effects. We first analyze the mechanisms of each emulsifier in an oil-based drilling fluid formulation and the filtration reduction mechanisms, taking into account the collapse-prone and abnormally high-pressure characteristics of shale formations. We undertake an experimental evaluation and optimization of polymeric surfactants, such as primary and secondary emulsions for high-performance oil-based drilling fluids. The design of rigid and deformable nano-micron plugging materials with a reasonable particle size range was achieved, and we obtained a low Oil—Water ratio and high-density oil-based drilling fluid system, with temperature resistance of 200 °C, an Oil—Water ratio as low as 70:30, compressive fracturing fluid pollution of 10%, and a maximum density of 2.6 g/cm3. The reuse rate reached 100%. The developed oil-based drilling fluid system with strong plugging, a high density, and a low Oil—Water ratio suitable for deep shale gas can effectively seal the well wall, reduce liquid invasion, prevent the wall from collapsing, reduce mud leakage, reduce the consumption of oil-based drilling fluid, improve the utilization rate of old mud, and reduce drilling costs.

Wellbore Stabilization Technology of “Fluid-Solid-Chemical Coupling” in Continental Shale Oil—A Case Study of Shale Oil in Block GL

During the oil shale drilling in Group Q of Block GL, the shale is prone to hydration, deterioration, sidewall exfoliation and frequent collapse, which affects the efficient exploration and development of shale oil. In order to reveal the mechanism of wellbore instability in the shale formation, the tectonic characteristics of shale are studied by combining microscopic and macroscopic methods, which identifies three key factors of physics, chemistry and mechanics about wellbore instability. Based on the analysis of earth stress and rock mechanics parameters, the experiment has established the prediction model of “fluid-solid-chemical coupling” collapse pressure of shale formation in Group Q, and calculated the safe drilling fluid density window for the horizontal wells of shale oil in Block GL by the prediction model. The main factors of wellbore instability in shale formation, deterioration characteristics and high density of oil-based drilling fluid on the well site is combined. The targeted plugging anti-sloughing and strong wetting agent were developed by using laser particle size instruments and pressure transmission experiments. A high thixotropy and strong plugging oil-based drilling fluid system is formed. The research results have been successfully applied in 16 horizontal wells of the shale oil test platform. The excellent rheological property, reliable plugging and bearing capacity and outstanding wellbore stabilization effect provides technical support for high-quality and efficient exploration and development of shale oil in Block GL. The “fluid-solid-chemical coupling” wellbore stabilization technology of continental shale oil formed in this study can provide a reference for the exploration and development of similar types of shale oil and gas reservoirs.

New HTHP fluid loss control agent for oil-based drilling fluid from pharmaceutical waste

In Oil-Based drilling fluid systems (OBM, for Oil-Based Mud) the oil phase is the major source of contamination and hydrocarbon pollution is, by far, the main concern. However, the release and accumulation of mud additives in the environment may be deleterious on grounds of volume and/or concentration. This paper describes a waste valorisation study from an antibiotic large-scale manufacturing for the preparation of a new drilling fluid additive (Fluid-Loss-Control agent: FLC) for OBM. This additive is environment-friendly, biomaterial in nature, and totally biodegradable and thus expected to have no detrimental effects on the surrounding environment and ecosystems. After product washing, heating, grinding, and screening, a cationic surfactant was used to improve fluid stability and filtration properties. Our results show that: According to drilling fluid requirements, the treatment of this pharmaceutical reject yields a product with good properties, i.e. satisfactory as far as thermal stability, filtration characteristics, and rheology property are concerned, - The pre-treatment of those products (according to their original state and particle size, as well as the type and concentration of added surfactant) enhances additive quality and shows good compatibility in drilling fluid systems, - The substitution of this new product for conventional additives affords good drilling fluid stability and performance under high temperature and high pressure (HTHP) conditions, economic, and environmental solutions to improve the environmental standing of OBMs further. • Providing effective environmentally acceptable fluid loss control. • New additive without damaging formation permeability. • Presentation of new fluid-loss-control agent from the pharmaceutical industry. • It is a by-product of an industrial antibiotic fermentation process.

Synthesis, aggregation behavior of alternating copolymer emulsifier in oil solution and its application in oil-based drilling fluids

In order to solve the emulsification problem of oil-based drilling fluids under high-temperature conditions, the copolymer emulsifier with the structure of alternating tertiary amine moieties and alkyl groups was synthesized by the reaction of N,N-dimethylethylenediamine and the alternating copolymer of maleic anhydride with 1-octadene (PMAO). The structure compositions and molecular weight of copolymer emulsifiers were characterized by FT-IR spectra, 1H NMR spectra, elemental analyse and multi-angle laser light scattering. The influence of tertiary amine moieties proportion in copolymer emulsifier on aggregation, interfacial activity, pH-response and emulsion stability were studied. The abundant presence of tertiary amine makes copolymer stabilize water-in-oil emulsion under neutral and weak alkaline conditions while destabilizing the emulsion under acidic conditions. Combining the above experimental data and the stability of water-in-oil emulsions prepared by the copolymer emulsifier, it was found that the emulsifier which has a high proportion of tertiary amine was indeed better at the performance of salt resistance under high temperature. When the copolymer emulsifier (D100) was used in an oil-based drilling fluid system, the electricity stability is greater than 1000 V and the filtrate volume is only 0.6 mL after aging at 232 °C for 16 h.

Research and Application of Evaluation Methods for Functional Characteristics of Oil-Based Drilling Fluid in Shale Gas Wells

Intelligent unconventional reservoir optimal production control technology is a comprehensive technology, involving geology, reservoir simulation, and efficient drilling and completion. Efficient drilling and completion provides a flow channel for unconventional oil and gas exploitation and a wellbore with good integrity for reservoir transformation, which is an important link in the efficient development of unconventional oil and gas. The application of industry standard method to evaluate the performance of oil-based drilling fluid has the problem of poor correlation. It cannot reflect the difference of performance among oil-based drilling fluid systems, which lacks the significance for field construction. Based on shale expansion, rolling dispersion experiment, and microporous membrane filtration loss test, the physicochemical mechanism of borehole wall instability in shale formation was investigated. The evaluation methods of shale lubrication, antiaccretion test, slake durability, buck hardness test, etc. are put forward, and the formula of oil-based drilling fluid is optimized. The lubrication and antiaccretion experiment method can effectively and intuitively characterize the cleaning and lubrication effect of drilling fluid on drilling tools. The slake durability evaluation method simulates the collision between drill cuttings and the drill string and well wall. The bucking hardness experiment is through testing the cuttings and the hardness change after drilling fluid action reflects its inhibitory effect. The new methods were used to evaluate the oil-based drilling fluid used in 4 wells in the Changning block. It was found that the drilling fluid of CN209H2 well adhered to the steel column with at least 0.41 g of cuttings; the recovery rate of the drilling fluid resistance of CN209H1 was up to 87.70%, and YX1200 oil-based drilling fluid plugging agent was selected through the microporous membrane experiment. In the process of drilling the well CN209H5, the new oil-based drilling fluid formulation improved the lubrication performance by 44%, accompanied by 95.48% recovery rate and less than 10 mL HTHP fluid loss at the same time. The research results show that the oil-based drilling fluid system optimized according to the new method can significantly inhibit shale hydration and dispersion and can effectively solve the problem of unstable performance of traditional oil-based drilling fluids in the Changning block.

Oil-Based Drilling Fluid Plugging Method for Strengthening Wellbore Stability of Shale Gas

Finding out the reasons for wellbore instability in the Longmaxi Formation and Wufeng Formation and putting forward drilling fluid technical countermeasures to strengthen and stabilize the wellbore are very crucial to horizontal drilling. Based on X-ray diffraction, electron microscope scanning, linear swelling experiment, and hot-rolling dispersion experiment, the physicochemical mechanism of wellbore instability in complex strata was revealed, and thus, the coordinated wellbore stability method can be put forward, which is “strengthening plugging of micropores, inhibiting filtrate invasion, and retarding pressure transmission.” Using a sand bed filtration tester, high-temperature and high-pressure plugging simulation experimental device, and microporous membrane and other experimental devices, the oil-based drilling fluid treatment agent was researched and selected, and a set of an enhanced plugging drilling fluid system suitable for shale gas horizontal well was constructed. Its temperature resistance is 135°C and it has preferable contamination resistibility (10% NaCl, 1% CaCl2, and 8% poor clay). The bearing capacity of a 400 μm fracture is 5 MPa, and the filtration loss of 0.22 μm and 0.45 μm microporous membranes is zero. Compared with previous field drilling fluids, the constructed oil-based drilling fluid system has a greatly improved plugging ability and excellent performance in other aspects.

Evaluation of Formation Damage of Oil-Based Drilling Fluids Weighted with Micronized Ilmenite or Micronized Barite

SummarySolids found in drilling fluids, particularly weighting materials, can cause significant formation damage by plugging of formation pores. This study investigates formation damage caused by using oil-based drilling fluid systems weighted by micronized ilmenite or micronized barite. Rheological properties of the oil-based-mud (OBM) systems were measured. High-pressure/high-temperature (HP/HT) static filtration experiments were conducted. A coreflood system was used to simulate dynamic conditions, allowing for drilling fluid circulation at the face of the core and measuring permeability damage. Computed-tomography (CT) scan analysis revealed formation damage and depth of solid invasion. The paper presents field applications of nondamaging micronized-ilmenite-based OBM, illustrating its advantages.

Development of Organic Soil Suitable for Biodiesel-Based Drilling Fluids

The oil-based drilling fluid system has the advantages of excellent lubricating performance, strong inhibitive ability, good sidewall stability and good temperature resistance, etc., however, which also has disadvantages of polluting the environment, easy to catch fire, and higher preparation cost, etc. In the development of biodiesel drilling fluid system, we no longer use diesel or crude oil, instead, it is replaced by biodiesel. Biodiesel also has better environmental friendliness, stronger biodegradability, higher safety performance and renewable advantage (Xin, 2005) while meeting specific requirements and achieving relevant performance. Biodiesel drilling fluid is more suitable for actual drilling operations for the more fragile ecology and higher demand environment. However, the organic soil on the market is basically developed for the white oil system. Therefore, we developed organic soil suitable for biodiesel systems by combining the actual situation of organic soil in the market through the measures of comparison, optimization, modification, etc.

Study on the multicomponent collaborative sealing mechanism of shale formations

Due to strong inhibitive ability, oil-based drilling fluid system was often the first choice of drilling fluids in the drilling operation of shale plays. However, borehole instability problems tend to occur most frequently in the drilling operation of horizontal well intervals. So the sealing mechanism of shale formation was of great importance to wellbore stability. Sealing effect of colloid particles, bridging and blocking effect of skeleton particles, plugging function of deformable particles and isolation effect of polymer were analysed, and multicomponent collaborative plugging mechanism was investigated. The results indicated that it could play an important role in plugging micropores and microfractures on shale surface to form a blocking layer with ultra-low permeability. This study can be helpful for the design of novel plugging agents for drilling fluids, and endow with economically and technically viable petroleum development and production.

Research on High Density Oil-Based Drilling Fluid and Application in the Southern Edge of Junggar Basin, China

The southern edge of the Junggar basin has broad exploration potential. However, high-frequency complex drilling accidents in this area lead to the reduction of the average drilling speed and the extension of the drilling cycle. The main geological reason is that this area was affected by the process and developed high and steep geological structure. The nappe formation with a large dip angle and poor stability developed along faults. The major rock type of this E2-3a formation is mud-stone which has strong water sensitivity and can be hydrated and dispersed easily, which leads to the wellbore shrinkage and the borehole collapse. In order to improve the drilling speed in the southern edge of the Junggar basin and accelerate the exploration and development process, the drilling fluids associated with drilling problems in this area were investigated in this paper by combing the geological information and historical drilling records. Because of the special characteristics of this formation, it is concluded that the water-based drilling fluids previously used in this area are not suitable to solve the complex drilling conditions; a high density oil-based drilling fluid system has been developed for this area by conducting studies in the laboratory initially and being tested in the field later. In addition, its rheology, stability and pollution resistance performances were evaluated. Results show that, the rheology, the stability and pollution resistance capacities of the drilling fluid satisfy the drilling requirements. The fluid was applied in well H101 and the results show that the ROP of section 311.1 mm of the well was increased by 763% compared to the wells drilled in the same area and the total drilling time of well H101 was reduced by more than 80%, which was a historic breakthrough of the drilling speed in the southern edge.

Study on the effect of polymeric rheology modifier on the rheological properties of oil-based drilling fluids

A new type of polymeric rheology modifier was synthesized by suspension polymerization, and the effect of rheology modifier on the rheological properties of oil-based drilling fluids was investigated. The results indicated that the obtained polymer had good capacity of improvement of shearing force of oil-based drilling fluids under high temperature and high pressure conditions. Moreover, the obtained polymer can improve the stability of oil-based drilling fluids greatly. As a result, the obtained polymer is a good rheology modifier for oil-based drilling fluids, and it can optimize oil-based drilling fluid system with good rheological properties, good static suspension ability for cuttings and environmental protection function. It can play an essential role in safe drilling jobs and improvement of drilling efficiency.

The use of grass as an environmentally friendly additive in water-based drilling fluids

Excellent drilling fluid techniques are one of the significant guaranteed measures to insure safety, quality, efficiency, and speediness of drilling operations. Drilling fluids are generally discarded after the completion of drilling operations and become waste, which can have a large negative impact on the environment. Drilling materials and additives together with drill cuttings, oil, and water constitute waste drilling fluids, which ultimately are dumped onto soil, surface water, groundwater, and air. Environmental pollution is found to be a serious threat while drilling complex wells or high-temperature deep wells as these types of wells involve the use of oil-based drilling fluid systems and high-performance water-based drilling fluid systems. The preservation of the environment on a global level is now important as various organizations have set up initiatives to drive the usage of toxic chemicals as drilling fluid additives. This paper presents an approach where grass is introduced as a sustainable drilling fluid additive with no environmental problems. Simple water-based drilling fluids were formulated using bentonite, powdered grass, and water to analyze the rheological and filtration characteristics of the new drilling fluid. A particle size distribution test was conducted to determine the particle size of the grass sample by the sieve analysis method. Experiments were conducted on grass samples of 300, 90, and 35 μm to study the characteristics and behavior of the newly developed drilling fluid at room temperature. The results show that grass samples with varying particle sizes and concentrations may improve the viscosity, gel strength, and filtration of the bentonite drilling fluid. These observations recommend the use of grass as a rheological modifier, filtration control agent, and pH control agent to substitute toxic materials from drilling fluids.

The Effectiveness of Cationic and Polymer Inhibitors on Shale

Maintaining the borehole stability while drilling oil and gas wells is a major problem when drilling through water sensitive formation. Drilling using oil-based drilling fluid is the most effective solution to control shale. Due to the increasing environmental constraints on the use of mineral oil-based drilling fluid system, expensive research has been studied to optimize oil well operations and minimize drilling cost using new water-based drilling fluid system. In this study, the effectiveness of three commonly used shale inhibitors were tested, where cationic polymer and KLA-Gard are cationic type inhibitors and PHPA is polymer type inhibitor. Two types of shale samples were used in this study, both were taken from Malaysia. Each shale sample represents different degree in swelling and dispersion characteristic. The testing procedures were employed for the shale reactivity evaluation, inhibitors’ performance evaluation, rheology and filtration loss effect evaluation as well as the character of the recovered shale from dispersion test. Result showed that the cationic type inhibitor is suitable to be used for swelling shale. For disperse shale, polymer type inhibitor is the best selection to be added in the drilling fluid system. The combination of cationic inhibitor used along with the polymer inhibitor showed reduction in dispersion and swelling tendency. It is also found that the cationic inhibitors showed well compatibility with other polymers in the ionic solution. Cationic inhibitors do not affect the rheology and filtration loss properties but polymer inhibitors affect these properties.

Mineralogical, microstructural and physiochemical characteristics of organic-rich shales in the Sichuan Basin, China

Although the Lower Silurian Longmaxi Formation shales in the Sichuan Basin have been widely investigated for their shale gas potential, detailed research on the differences between the Upper Longmaxi Formation (ULF) shales and the Lower Longmaxi Formation (LLF) shales is still scarce. In this study, the divergent properties of the LLF and ULF shales in the Sichuan Basin of China were investigated, including mineralogical characteristics, microstructural characteristics and physiochemical characteristics. The mineralogical characteristics and their influences, the relationships between the specific surface area, pore volume and TOC, mineralogical compositions, and the influences of microstructure on the development of the Longmaxi Formation (LF) shale gas reservoir were explored and discussed. The results indicate that the LF shales mainly consist of quartz and clay minerals. The ULF shales have higher clay minerals contents and lower quartz contents, whereas the LLF shales have lower clay minerals contents and higher quartz contents. Compared with the ULF shales, the LLF shales have higher TOC contents, which results in higher specific surface area and total pore volume, a larger fractal dimension, a more complex pore structure and thus a greater adsorption capacity. The LLF shales have weaker hydration swelling and stronger brittle features, indicating that the LLF shales would have good wellbore stability and good hydraulic fracturing. Because of fractures in the LF shale formation, designs for oil-based or water-based drilling fluid systems need to consider sealing technologies. For water-based drilling systems, hydration inhibition should be considered, especially for the ULF shale formation.

Nanoplugging Performance of Hyperbranched Polyamine as Nanoplugging Agent in Oil-Based Drilling Fluid

A hyperbranched polyamine was synthesized by self-condensing vinyl polymerization with divinyl sulfone, N-phenyl-p-phenylenediamine, by A2+BB2'approach. The hyperbranched polyamine was characterized by FT-IR, TGA, and phase analysis light scanning. Average grain diameter of hyperbranched polyamine was 36.7 nm. Hyperbranched polyamine has good thermal stability. Hyperbranched polyamine (HBPA) was employed successfully as nanoplugging agent in oil-based drilling fluid system, which could plug nanopore formation in shale formation. HBPA has a little effect on rheological properties of oil-based drilling fluid and theFLAPIandFLHTHPdecreased dramatically with an increase of hyperbranched polyamine. Emulsion-breaking voltage has a slight increase, which is beneficial to maintain stability of oil-based drilling fluid. When the HBPA concentration is greater than 1 wt%, plugging rate of oil-based drilling fluid for artificial core is close to 100% and the permeability recovery value can reach 99.7% after adding 1 wt% HBPA, which prove that HBPA has an excellent plugging performance.

Purification and Physio-chemical Characterization of Glycerol By-product of Palm Oil Biodiesel Industry as a Potential Base Fluid for Synthetic Oil-based Drilling Fluid System

Purification and Physio-chemical Characterization of Glycerol By-product of Palm Oil Biodiesel Industry as a Potential Base Fluid for Synthetic Oil-based Drilling Fluid System

Use of Rubber Seed Oil as Base Fluid in the Formulation of Oil-Based Drilling Mud

An oil-based drilling fluid system was formulated using rubber seed oil as base oil. Rubber seed oil was chosen because its aniline and flash points fall within the range of oils used as base oil. It is also locally available and easily affordable. The rheological (flow) properties of the rubber seed oil-based drilling fluid system were measured and results obtained show that the 10-sec and 10-min gel strength values for the formulated mud are 210lb/ft2 and 211lb/ft2 respectively while the mud density, plastic viscosity and yield point values are 10.60ppg, 1cP and 328lb/ft2 respectively. Comparison with the properties of a commercial oil-based drilling fluid show that the formulated mud has a high penetration rate and hole cleaning ability and so is effective in drilling operations although some disadvantages were observed.

A “Dual Protection” Drilling Fluid System and Its Application

Excellent drilling fluid techniques are one of the significant guarantee measures to insure the safety, quality, efficiency, and speediness of drilling operations. However, these drilling fluids are generally discarded and become wastes, which have the largest number and the largest influence on the environment after the completion of drilling operations. These drilling materials and additives together with drilling cuttings, oil, and water entered formations constitute waste drilling fluids, which ultimately went into soil, surface water, groundwater, and air. Among all kinds of drilling fluid systems that have been developed and applied at present, acrylic acid and its derivatives drilling fluid system and polysulfonate drilling fluid system are widely used. Environment pollutions are serious in complex wells or high-temperature deep wells, and even in oil-based drilling fluid systems. This article is based on lots of laboratory experiments on the chemical toxicity, biological toxicity, and biodegradability of drilling fluid additives that are mostly used in domestic fields screened out fluid loss additives, inhibitors, anti-sloughing agents, lubricants and so on that fit a “dual protection” drilling fluid system. In addition, this article developed a dual protection drilling fluid system that met the requirements of safety, quality, efficiency, and speediness of drilling engineering; could reduced the pollution on environment in maximum; and could protect both hydrocarbon reservoir and environment.

Effect of Drilling Fluid Systems and Temperature on Oil Mist and Vapour Levels Generated from Shale Shaker

Workers in the drilling section of the offshore petroleum industry are exposed to air pollutants generated by drilling fluids. Oil mist and oil vapour concentrations have been measured in the drilling fluid processing areas for decades; however, little work has been carried out to investigate exposure determinants such as drilling fluid viscosity and temperature. A study was undertaken to investigate the effect of two different oil-based drilling fluid systems and their temperature on oil mist, oil vapour, and total volatile organic compounds (TVOC) levels in a simulated shale shaker room at a purpose-built test centre. Oil mist and oil vapour concentrations were sampled simultaneously using a sampling arrangement consisting of a Millipore closed cassette loaded with glass fibre and cellulose acetate filters attached to a backup charcoal tube. TVOCs were measured by a PhoCheck photo-ionization detector direct reading instrument. Concentrations of oil mist, oil vapour, and TVOC in the atmosphere surrounding the shale shaker were assessed during three separate test periods. Two oil-based drilling fluids, denoted 'System 2.0' and 'System 3.5', containing base oils with a viscosity of 2.0 and 3.3-3.7 mm(2) s(-1) at 40°C, respectively, were used at temperatures ranging from 40 to 75°C. In general, the System 2.0 yielded low oil mist levels, but high oil vapour concentrations, while the opposite was found for the System 3.5. Statistical significant differences between the drilling fluid systems were found for oil mist (P = 0.025),vapour (P < 0.001), and TVOC (P = 0.011). Increasing temperature increased the oil mist, oil vapour, and TVOC levels. Oil vapour levels at the test facility exceeded the Norwegian oil vapour occupational exposure limit (OEL) of 30 mg m(-3) when the drilling fluid temperature was ≥50°C. The practice of testing compliance of oil vapour exposure from drilling fluids systems containing base oils with viscosity of ≤2.0 mm(2) s(-1) at 40°C against the Norwegian oil vapour OEL is questioned since these base oils are very similar to white spirit. To reduce exposures, relevant technical control measures in this area are to cool the drilling fluid <50°C before it enters the shale shaker units, enclose shale shakers and related equipment, in addition to careful consideration of which fluid system to use.