Query: Pickering emulsion  Oil-based drilling fluid 

title: Polymer Drilling Fluids Emulsions (PDFE) A Review
abstract: Polymeric drilling fluids emulsions (PDFE) are very important because they are used as drilling fluid systems used in modern drilling operations. For low pressure and exhausted gas and oil reservoirs Oil in water (o/w) emulsion polymeric drilling fluids are used however for drilling completion and work over high pressure gauge wells Water in oil (w/o) invert emulsion polymeric drilling fluids are preferable. The stability of polymeric drilling fluids emulsions systems are possible as a result suitable chemical components called surfactants which creates good emulsion stability. The rheological and filtration properties are controlled by polymeric materials and bridging agents. This paper is a review on the recent developments and trends as new technologies emerge in polymeric drilling fluids emulsion and their level of efficiencies in drilling gas and oil wells. At times the mud components serve as soil supplement or agricultural aid. A lot of work needs to be done to popularise both drilling and waste problems. Some programmes have already been adopted to bring together economic and environmental considerations in drilling practices. A lot has been done in exploring waste reducing technologies. Pre treatment of emulsion muds before disposal is easier and lower in cost than oil based muds. Oils can be removed from the cuttings with the help of mechanical cuttings dryers and thermal desorption units. As per a recent developed technique, oil from drilled cuttings can be recovered by liquefied gas extraction technique. This paper touches not only on the progress made in drilling fluid technology but also on the environmental impact of the drilling fluids at the drilling sites.

title: Research and Application of New Type Drilling Fluid at Abroad
abstract: Research and applications of 3 kinds of drilling fluid systems at abroad were reviewed.The first type was water based drilling fluids(WBD),which typically included environmental friendly WBD,anti sloughing WBD,clay free WBD,anti high temperature WBD,and aphron WBD.The second type was oil based drilling fluids(OBD),which typically included whole OBD,OBD with zero filter loss,low toxic OBD,low solid OBD,anti high temperature OBD,and reversible emulsion OBD.The third type was synthetic based drilling fluids with anti high temperature and constant rheology characteristics.

title: The use of novel chemistry to minimize the interaction of the water based fluid with water sensitive shales is the key to achieving targets of greater levels of wellbore stability, hole gauge, reduced dilution rates and improved drilling
abstract: The more stringent environmental demands together with an increasing focus on drilling performance and economics has created a push towards a greater usage of new and more highly inhibitive water based drilling fluids, often to replace invert emulsion fluids. The use of novel chemistry to minimize the interaction of the water based fluid with water sensitive shales is the key to achieving targets of greater levels of wellbore stability, hole gauge, reduced dilution rates and improved drilling economics. One unfortunate result of the use of many of these water based drilling fluids has been an increase in the incidence of bit balling and cuttings accretion, which has resulted in lost time, reduced drilling rates and often expensive remediation operations. This paper reviews recent developments in the areas of both the remediation and prevention of bit balling and shale accretion in water based drilling fluids. The paper describes the mechanism of bit balling and cuttings accretion, the influence of clay type, fluid chemistry, and drilling parameters and also gives guidelines for minimization of bit balling potential. In addition to discussing testing protocols for evaluation of bit balling potential, field results obtained from usage of a modern day bit balling prevention additive are presented.  When using oil based or synthetic based drilling fluids, there are often associated costs for cuttings treatment, waste stream processing and compliance testing, all of which must be taken into consideration, as well as the typically higher cost per unit volume of these fluids. However the higher operational costs associated with the use of invert emulsion fluids can sometimes be offset by higher rates of penetration (ROP) and a lower risk of operational problems compared with the majority of water based drilling fluids Over the past few years, introduction of new water based fluid systems and specific additives have been successful in greatly reducing the incidence of wellbore stability problems. The main causes of non productive time observed with the latest water based fluids are issues related to bit balling, agglomeration and accretion of drilled cuttings. Slow ROP, high torque and drag, high overpull on tripping, and potential for wellbore packoff and lost circulation are the most immediate problems. Shale cuttings profiles can be evaluated in terms of soil mechanics. From initial stages as a relatively dry claycontaining material, shales will adsorb water (liquids) in an attempt to relive their internal stresses. As water is adsorbed, the shales reach a plastic limit where the sticking tendency of shale is very high therefore leading to all the problems described above. The primary differences between invert emulsion fluids and water based fluids that decrease any tendency for bit balling and accretion in the former are the very high capillary pressures in shales that prevent uptake of base fluid, this inhibiting shale sticking, plus the wetting of shale and steel surfaces with a non aqueous film that will hinder any shale sticking.  Theories based on the plasticity of the clays explains the accretion that occurred. The clay plasticity concept proposes that the rate of hydration of a shale is slowed down such that the cuttings remain in a plastic state over a longer period of time. This plasticity state is believed to contribute towards cuttings becoming molded onto the steel parts of the bottomhole drilling assembly (BHA) and being plastered onto the walls of the wellbore. By using a much less inhibitive drilling fluid, shale cuttings would normally hydrate quickly and tend to be less sticky as they continue to adsorb water thus quickly passing through the plastic stage and into a liquid stage where the shale has little cohesive strength, and readily disperses. The Attenberg limits of a clay are defined as the liquid limit, plastic limit, and plastic index and are fully described in published literature. The liquid limit (LL) is the moisture content, expressed as a percentage by weight of the oven dry clay, at which the material will just begin to flow when jarred slightly. The plastic limit (PL) is the lowest moisture content, expressed as a percentage by weight of the oven dry clay, at which the soil can be rolled into threads one eighth of an inch in diameter without breaking into pieces. The plastic index (PI) is the difference between the liquid limit and the plastic limit. It gives the moisture content range through which a soil is considered to be plastic. Through extensive studies on a number of clay types, it was determined that for clays that are montmorillonite in nature, the structure of the clay mineral is the most important factor in determining the properties of these clays in contact with aqueous media. The cation associated with the AADE 11 NTCE 28 The Prevention and Cure of Bit Balling in Water Based Drilling Fluids Sashikumar Mettath, Emanuel Stamatakis, Steven Young, and Guido De Stefano, M I SWACO 2 Sashikumar Mettath Emanuel Stamatakis, Steven Young and Guido De Stefano AADE 11 NTCE 28 montmorillonite can alter the structure established by the clay mineral, but is of secondary importance in the hydration behavior. The liquid limit of montmorillonite clays will increase with an increase in the hydrated radius of the predominant clay cation. For kaolinitic clays, the electrical attractive forces and particle orientation in the fabric play a prominent role. Thus kaolinite clays with a high degree of flocculation will have larger void spaces and exhibit higher liquid limit values, whereas those with a low degree of particle flocculation will have smaller void spaces and exhibit lower liquid limit values. Depending on the mineralogical makeup of a shale, the behavior in the presence of a water based drilling fluid can be entirely different depending on whether the primary clay mineral is kaolinite or montmorillonite. The conclusion of many studies into clay and shale behavior can be summarized by stating that both the liquid limit and plastic limit of a shale are primarily a function of the percent clay fraction, the clay mineral type and the type of associated cations present. The ratio of PL/LL was seen to increase according to clay type: (Na montmorillonite Illite Kaolinite) and to the valency and hydrated ionic radius of the associated cation: (Na K <Ca <Mg <Fe <Al) The presence of non clay minerals in a shale will reduce the magnitude of the PL and LL, but the ratio will remain the same. In order for cuttings accretion to occur, the following three criteria must be met: 1. The shale must have sufficient moisture to be in a plastic state when in contact with the drilling fluid. Deformation of the shale structure can readily occur when the plastic state is achieved. Note that some shales can be encountered that are naturally in the plastic state and do not need to take moisture from the drilling fluid. 2. The surface of the shale cutting must be sticky enough to form a bond with other surfaces with which it makes contact. This can be contact with any steel surface of the BHA or with a wellbore surface. The "stickiness" of the shale surface can be enhanced by rapid surface water absorption from the drilling fluid, and also by some drilling fluid polymeric additives. 3. The surfaces of the cuttings must be pushed together with sufficient force to deform the clays and create a bond. This force can be mechanical (e.g. contact of cuttings with a drilling assembly) and can also be hydraulically generated (e.g. forcing cuttings through a narrow aperture) To evaluate these influences on bit balling and cuttings accretion further, a full suite of laboratory testing was conducted. LABORATORY STUDIES Preserved outcrop shale samples were used in the laboratory studies. Shales with a broad range of composition and reactivity were selected from highly swelling (Lillebaelt clay) through mixed (Oxford clay) to highly dispersive (Arne clay) a) Lillebaelt clay is a fine grained, high montmorillonite, swelling clay sourced from an outcrop in Denmark. b) Oxford Clay is a swelling and moderately dispersive shale of Jurassic origin sourced from an outcrop in southern England. c) Arne clay, a ball clay with high kaolinite content, is highly dispersive in contact with water and is sourced from an outcrop in southern England. Analysis of these outcrop shales by X ray diffraction is shown in Table 1 below: Table 1: XRD analysis of Outcrop Shales Clay Quartz Plagioclase K fspar Calcite Arne 14.8 1.4 1.5 0.9 Lillebaelt 3.6 1.2 2.6 21.8

title: DRILLING FLUIDS FOR HIGH TEMPERATURE WELLS
abstract: It is possible that the large oil and gas fields have already been discovered. The new discoveries are smaller, remote, deep water, or buried deep underground. Drilling deep wells often have to face the challenges from high temperature. It is especially challenging for drilling fluids to maintain desirable properties under a thermally demanding environment over extended drilling time. This paper surveys the worldwide field cases of drilling fluids for high temperature wells. According to field experiences, oil based mud and emulsion mud provides the best wellbore stability, thermal stability and rate of penetration (ROP) Water based formate mud is an alternative to oil based mud at a lower cost and less environmental impact. Formate mud also produced good wellbore integrity and good ROP. Foam mud is most suitable for drilling low pressure formations with wellbore instability issues. The field case demonstrated foam mud was successfully implemented in a high temperature and low pressure well.

title: Conventional and Eco Friendly Hydraulic Fracturing Fluid Additives: A Review
abstract: The purpose of this paper is to create a starting point for research into using friendly and biodegradable waste material as supportive items for hydraulic fracturing fluids and additives. Conventional fluids and additives, although they can be effective, they pose serious threats to work personnel and public health and to the environment. Conventional fluids and additives can also be very costly. These risks and concerns should drive the oil and gas industry to pursue alternative options, safer and cheaper options, from conventional fracturing fluids and additives. Some waste materials provide this opportunity. It is apparent through many forms of research that waste materials are readily available globally making it easy and cheap to obtain. A driving force for this research was research previously done on finding alternative additives for drilling fluids. Researchers have proven that some of the waste materials, such as food waste, grass waste, palm tree waste, among many others, can and should replace or at least boost conventional drilling fluids and additives through a series of experiments and tests. Not only are these materials easier and cheaper to obtain, but they are also efficient and safer for both the environment and people. The same could be said for alternative hydraulic fracturing fluids and additives if proper research is done. The strides made in finding alternatives for drilling fluid additives have pushed the revolutionizing of the oil and gas industry, acting as a catalyst for the research into alternative hydraulic fracturing fluids and additives. In this work, a more thorough investigation into conventional fracturing fluids and their downfalls regarding price and health and environmental concerns are illustrated as well as the function of the main fracturing fluids; water fracs, linear gels, crosslinked gels, oil based fluids, and foam/poly emulsions. Throughout this paper, it becomes apparent that the oil and gas industry should attempt replacing or decreasing conventional fracturing fluids additives because of the negative influences they have on profit, people's health and safety, and the environment.

title: Environmental Impact Evaluation of a Safe Drilling Mud
abstract: Due to increase in environmental legislation against the disposition of oil based mud and an increase in environmental awareness, there is need for drilling companies to come up with a superior drilling mud with little or no aromatic content, which is biodegradable and environmentally friendly which poses no health hazard to oilfield workers and the host community. For this study, oil extracted from the non food plant seeds (jatropha and canola seeds) were used as the base fluid for drilling mud samples in laboratory, oil in water emulsion was made using oil water ratio of 70 to 30. 200ml of oil; 350ml of water, 50g of bentonite and barite was finally added to build the density up to 10ppg. Three mud samples were formulated with three different based fluids which are diesel, jatropha and canola oil based mud samples. Different mud laboratory tests such as toxicity, filtration, pH, viscosity and density were carried out on the three samples to ascertain their suitability properties for drilling operation and their degree of safety to the environment. The results obtained show that jatropha has the lowest viscosity, which imply less resistance to flow and lower pressure losses. The outcome of toxicity test confirmed jatropha to be safer and less harmful to plant life and soil micro organism while diesel proved to be most toxic among the three samples. The overall results obtained from laboratory tests indicate that jatropha oil based mud pose great chance of being among the technically and environmentally viable replacements for convectional diesel oil based mud. The study serves as one of the ending solution to the environmental problem associated to oil based drilling operation especially in deep water exploitation.  Oil based drilling fluids have some advantages that make them especially desirable for drilling certain types of formations. Oil based muds generally provide better performance in very hot or very cold environments. Oil based muds cause fewer problems when drilling shale formations and allow drilling of salt zones with minimal dissolving of salt. However, there are greater costs and potential pollution problems which make it a bad choice for environmentally sensitive areas Drilling mud is in varying degrees of toxicity. It is difficult and expensive to dispose in an environmentally friendly manner. Protection of the environment from pollutants has become a serious task. In most countries like Nigeria, the drilling fluids industries have had numerous restrictions placed on some materials they use and the methods of their disposal. Now, at the beginning of the 1990's, the restrictions are becoming more stringent and restraints are becoming worldwide issues. One of the products that have been particularly affected by restrictions is oil based mud. This fluid has been the mud of choice for many environments because of their better qualities. Potential liability, latent cost, and negative publicity associated with an oil mud spill are economic concerns. There is the urgent need for the drilling fluids industry to provide alternatives to diesel oil based mud. Researches and surveys have been on track for the past two to three decades in response to harmfull impact of diesel based mud on enviroment, and have come up with the new trend in the energy industry with the emergence of the use of plant oils as diesel substitutes. Over the years, plant oils have become increasingly popular in the raw materials market for diesel substitutes. The most popular being: Rapeseed oil, Jatropha oil, Mahua oil, Cottonseed oil, Sesame oil, Soya bean oil, palm oil etc. This brings about the importance of agro allied intervention in the energy industry. In recent times, following the outcomes of the past researches carried out, synthetic oils are now considered more environmentally friendly than the conventional diesel or mineral oil based mud. Among other researchers, Bailey et al in 1986 examined fluid viscosities of muds formulated with a low toxicity mineral oil

title: Drilling Induced Near Wellbore Formation Damage: Drilling Mud Filtrate and Solids Invasion and Mud Cake Formation
abstract: Under and overbalance drilling, near wellbore formation damage, vertical versus horizontal wells, formation damage caused by drilling and completion fluids, effect of drilling fluids on shale stability, and mitigation of formation damage induced by completion fluids and crude oil emulsions are discussed. The fundamental processes and their mathematic formulation necessary to develop prediction and simulation models are reviewed for assessment of the damaged zone, filtrate and fines concentrations, fluid saturations, filter cake thickness, and mud loss during drilling. The models for prediction of damage depth, simulation of the single and two phase flow situations in the formation with water or oil based drilling mud cases, and mud invasion into naturally fractured formations are described. External particle invasion prior to filter cake buildup and its effect on the formation damage by particle invasion and retention and filter cake formation are explained. These models are demonstrated by various applications, including the estimation of the near wellbore fluid saturations and resistivity profiles, which are necessary for accurate well log interpretation, and the drilling mud loss into naturally fractured formations.

title: AADE 18 FTCE 066 Monetizing Low Value Streams to High Value Emulsifiers Performance Analysis and Field Application
abstract: In today's era of low priced oil, operators and service providers sustain business by reducing their cost foot prints. A reduced cost foot print may involve lower pricing on existing or fit for purpose services and products, as well as compromised performance on the services and products. In this publication, we present high value primary and secondary emulsifiers for invert emulsion (oil based) drilling fluids developed from a refinery side stream of the crude tall oil (CTO) We managed the composition variation challenge by setting precise specifications on this side stream and connecting aspects of product composition with desired performance in the drilling fluid application. This side stream was derivatized under engineered reaction conditions to develop the present high value primary and secondary emulsifiers without compromise in performance. Overall, detailed testing was performed to determine the emulsifier performance in different base oils (mineral oil and diesel) at different mud weights (12 to16 ppg) characterized by rheology and HTHP fluid loss. The developed primary and secondary emulsifiers performed on par or outperformed the industry available emulsifiers tested in this study. The primary emulsifier demonstrated low pour points, low product viscosity and high flash points as compared to the industry standards. The field application of this primary emulsifier will be presented. On the other hand, the secondary emulsifier provided a highly solids tolerant, oil based fluid as compared to the industry standards.  The rotary rig count today in the U.S. remains less than half of what it was in 20141. The U.S. Energy Information Administration (EIA) reports that the rig and drilling costs make up 15 percent of the cost of drilling and completing the well2. Also, the drilling costs per unit depth has been declining continually since the highs of 20122. These pressures cause operators to restructure and streamline operations to improve drilling efficiency. Every drilling budget, regardless of target formation, comprises the drilling rig, drill string, fluid system, casing and cement. Our focus in this paper is to improve the drilling efficiency of invert emulsion fluid (IEF) systems with the use of efficient emulsifiers. Emulsifiers are a small portion (typically from 1 to 6 percent V/V) in the invert emulsion fluid but perform significant functions during the drilling process such as: Stabilize the invert emulsion. Maintain stable suspension. Maintain stable rheology. Oil wet the drilled solids. Maintain controlled fluid loss to the formation. Maintain shale inhibition and stability. During this research project, we developed: A high value primary emulsifier (HVPE) that delivered a tight invert emulsion, thus it was more efficient at controlling high pressure high temperature (HPHT) fluid loss (FL) than the industry available primary emulsifiers (PE) Also, the HVPE had lower pour points than the industry PE, thereby making it easier to handle even in colder temperatures. A highly solids tolerant, high value secondary emulsifier (HVSE) that imparted controlled (low) rheology to IEF in the presence of high concentrations of simulated drill solids. The advantages of this highly solids tolerant secondary emulsifier are: It can deliver low equivalent circulating density (ECD) fluids even at high concentrations of drill solids. It can reduce the treatments needed to control high rheology and thereby improve the working longevity of the fluids. The emulsifiers developed in this research were made from one of the variable side streams of the CTO distillation process. CTO is an acidulated product from sulfate black liquor skimming's which on distillation typically gives five product streams3: 1. Tall oil fatty acids (TOFA) that comprise ~30 35% 2. Tall oil rosin (TOR) that comprises~30 40% 3. Distilled tall oil (DTO) that comprises~5 10% 4. Tall oil heads that comprise ~5 10% 5. Tall oil pitch that comprises~15 40% Therefore, to provide these products streams, several variable side streams (VSSs) are produced. The current paper describes successful efforts to monetize the remaining fatty acid in one of these VSSs and manage variable properties to AADE 18 FTCE 066 Monetizing Low Value Streams to High Value Emulsifiers: Performance Analysis and Field Application Shadaab S. Maghrabi, Delores Smith, Aaron S. Engel, Jennifer Henry and Joseph Fandel, Ingevity Corporation 2 S.S. Maghrabi, D. Smith, A.S. Engel, J. Henry and J. Fandel AADE 18 FTCE 066 provide products that perform consistently. The variability in an important chemical property (used as a quality control specification for TOFA) for this VSS is presented in  The variability was determined by the subtracting individual batch values from the average of this chemical property. The contents of this paper are arranged as follows: Development of high value primary emulsifier (HVPE) Comparison of HVPE with industry available PE Field data of HVPE Based IEF used on a well Development of high value secondary emulsifier (HVSE) Data analysis and comparison with industry SE Advantages of low (controlled) rheology in the presence of high volume of drill solids Performance of the HV emulsifier package in various fluid systems. Performance in two mud weights 16 ppg and 12 ppg Performance of HV emulsifiers in a mineral base oil Performance of HV emulsifiers in different fluid type gilsonite based FLA Materials and Methods The fluids were mixed in stainless steel mixing cups on a five spindle multimixer model 9B having a rotational speed of 11500 rpm with sine wave impeller blade No. 9B29X. The fluids were aged in HTHP stainless steel aging cells and hot rolled in a model 5 roller oven from OFITE at the desired temperature for 16 h. The rheology of the fluids was determined on a standard OFITE oilfield viscometer as per API 13B 2. The rheology of the fluid was characterized in terms of the Bingham plastic viscosity (PV) Bingham yield point (YP) and gels minutes which were determined as per API 13B 2. The temperature was controlled with an electrically heated thermocup. In situations where the 600 rpm dial reading was not measurable due to instrument limitations, it was estimated by extrapolation with the Herschel Bulkley rheological model. The emulsion stability (ES) was determined on an Electrical Stability Tester model 23E from FANN. HPHT fluid loss was determined on a 500 ml HPHT filter press assembly for duration of 30 minutes as per API 13B 2 recommendations. The additives used to mix the fluids in this study were: Base oil: diesel and mineral oil Alkalinity control agent to activate the emulsifiers FLAs to maintain fluid loss control: polymeric FLA, amine treated lignite and gilsonite FLA Viscosifiers to maintain viscosity and suspension: polymeric viscosifier, high quality organoclay and economical organoclay PE: HVPE and industry available PE 1, PE 2, PE 3 and PE 4 SE: HVSE and industry available SE 1, SE 2 and SE3 Simulated drill solids CaCl2 for water phase salinity (WPS) Weighting agent to adjust density of the fluid Results and Discussions Development of High Value Primary Emulsifier A survey of the on shore drilling market in the U.S. showed that most of the IEFs use diesel fuel as the base oil. A 12 lb/gal (ppg) diesel fluid system was chosen as the screening formulation for the HVPE development, as shown in Table 1. The HPHT fluid loss was considered the most significant parameter for the HVPE development. A lower HPHT fluid loss with no water in the filtrate was considered a sign of a good emulsifier with a fluid loss of less than 7 mL at 6 lb/barrel (ppb) PE concentration was preferred. In a laboratory experiment, 1 ppb refers to 1 g in 350 mL of the fluid. Since viscosifiers and FLA influence the HPHT fluid loss, concentrations of these were maintained at a necessary minimum in this screening formulation. The screening formulation in Table 1 was used to optimize the reaction process parameters. Some of the reaction process parameters investigated for optimization were: Reaction temperature Reaction time Reactant concentrations and types Catalyst concentration Reactant specifications Product specifications Table 2 provides the four batches of the HVPE made with the optimized reaction process. These HVPE batches were made with four different batches of the VSS. These batches of VSS had different numbers of standard deviation (s) distances from the average for the important chemical property as discussed previously. It was observed that these batches of the HVPE gave less than 7 mL with no water at 6 ppb concentration. In addition, the fluid loss at 5 ppb was low. The pour points of HVPE batches were all less than 0oC implying that these are good candidates for cold climate sites. Comparison of HVPE with Industry Available PE In Table 3, a comparison between the HVPE and Industry PE 1, PE 2, PE 3 and PE 4 in the screening formulation is shown. Analysis showed that: At 6 ppb, only the PE 1 with fluid loss of 6.6 mL came close to the fluid loss performance of HVPE At 5 ppb, the PE 1 gave fluid loss of 7.8 mL with 0.3 mL water as compared to 4.0 mL for the HVPE All the other industry PEs gave high HTHP fluid loss. In Table 4, the product physical properties of the HVPE, PE 1, PE 2, PE 3 and PE 4 are compared. Analysis of the data shows that: HVPE had a low viscosity, thus it is easy to pour in general, particularly as compared to PE 1. The HVPE needs no dilution with solvents for application at the mud plant or rig site. AADE 18 FTCE 066 Monetizing Low Value Streams to High Value Emulsifiers: Performance Analysis and Field Application 3 The low pour points of the HVPE present it as a good candidate for use in cold climates, particularly compared to PE 1 and PE 2.

title: AADE 18 FTCE 037 Transitions from Diesel Muds Options Properties and a Proposal
abstract: The most common drilling fluid system for land based unconventional applications in the United States remains a diesel based invert emulsion. While studies show this base fluid meets requirements for exposure to personnel, advances in refining technology offer an opportunity to improve conditions for personnel and the environment with a transition to new base oil alternatives. This paper will discuss these advancements as well as recommendations for base oil properties that improve working conditions at the rigsite and lower the potential risks to the environment from exposure. With millions of dollars of dieselbased drilling fluid in inventory, an economic analysis reviews the timetable to convert this inventory over to new base oil systems. The authors will share experience with similar transitions. Through a comprehensive review of the options discussed, the authors are seeking to initiate a conversation within the industry to generate consensus on the necessary properties and requirements that would result in a cost effective transition if and when operators choose to enhance the health and safety profile of invert emulsion drilling fluid systems in the U.S. unconventional market.  Diesel remains a common, low cost option for non aqueous drilling fluids and it is approved in many locations throughout the United States. While it remains an acceptable option, enhancements in refining continue to narrow the cost gap between diesel and mineral oils where lower toxicity options become more practical. Demand for diesel alternatives grows as drilling operations expand near environmentally sensitive and/or residential areas, operators tighten internal policies regarding raw material consistency, and as they seek to enhance their profile as a greater steward of the environment. In the midst of requests for alternatives comes confusion defining the differences among a number of options. While the term "synthetic" is traditionally associated with "better" it is important to focus on advantages relative to diesel and specifically identify and quantify key favorable properties inherent to diesel alternatives. Overview and History The history of alternative base oils for drilling fluids has its origins in the offshore market. In the early 1990's onsite discharge of cuttings using oil based muds was banned, requiring the transition to synthetic based muds to avoid the cost of cuttings transport to onshore disposal sites. Requirements varied by jurisdiction; however, the primary driver focused on environmental impact, particularly discharge and seabed accumulation of cuttings. 1,2 Additional standards consider exposure to personnel, including enclosed areas such as pit rooms and the shakers. In the United States, many land applications still allow the use of diesel. The cost and availability of diesel makes it the base fluid of choice, where permitted. Beyond local regulations, alternative base oils are used for their perceived health and safety benefits. Near populated areas, some operators have employed diesel alternatives to minimize odors. 4 Base Oil Production Base oils are manufactured through a variety of processes, ranging from crude oil refining to chemical synthesis. These processes vary in complexity and associated cost. Products may be blended or further modified to achieve key properties. In many cases, nearly identical molecules are derived from different processes. Historically, refining technology was cheaper but left trace impurities not seen with chemical synthesis processes. With the advent of stricter regulations for fuels, processing technology can now dramatically reduce or eliminate these trace impurities. Definitions of mineral oils versus synthetics are inconsistent between regulatory bodies, creating significant confusion. Diesel is universally considered an oil based drilling fluid. Other categories include mineral oils, enhanced mineral oils and synthetics. Generally speaking, the manufacturing process is a key factor in defining a base oil category; however, highly refined materials with treatment processes offer the same molecules with potential for trace impurities. Materials produced with purely synthetic processes generally cost more, but have nearly all impurities removed. Mineral oil and synthetic materials include paraffins, olefins, and esters. Molecular structure is noteworthy as it impacts various performance factors. AADE 18 FTCE 037 Transitions from Diesel Muds: Options, Properties, and

title: Test Methodology Optimizes Selection of Fluids for Gasfield Development
abstract: This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 195601, "Systematic Selection of Drill In and Completion Fluids for Development of the Dvalin High Temperature Gas Field," by Oliver Czuprat, SPE, Bjorn Olav Dahle, and Ulf Dehmel, DEA, et al. prepared for the 2019 SPE Norway One Day Seminar, Bergen, Norway, 14 May. The paper has not been peer reviewed. For the development of the Dvalin high pressure/high temperature (HP/HT) gas field in the Norwegian Sea, a completion scheme using standalone screens is planned. To secure maximum cleanup and productivity, even after long term suspension, comprehensive laboratory testing was performed to evaluate specific properties from drilling and completion fluids at downhole conditions. The complete paper details the results of all test phases. With the test methodology, several proposed mud system candidates were disqualified at an early stage, thus saving time and cost for subsequent formation damage testing and complementary analytics.  Formation damage is believed to have caused difficulties in modular dynamic tester sampling in the high permeability zone of Dvalin West. The damage mechanism has been investigated in a study that revealed both fluid systems to have good fluid loss control properties, as observed in drilling operations. However, both systems showed damage potential. The extent of damage is more pronounced in  The field development plan calls for four producing wells to be drilled (two in each structure) Prevention or, realistically speaking, minimization of impaired production as a result of formation damage has been identified as a priority. A completion scheme with standalone screens requires additional specific properties from drilling and completion fluids at downhole conditions. The production facilities will be commissioned after the completion of drilling, and there are no provisions for handling cleanup flow through pipeline and topsides. Thus, all wells will be cleaned up to a temporary test plant on board the drilling rig. The lag time between drilling the wells and cleaning them will be 2 3 weeks, underlining the necessity of a drilling mud that is stable over a significant period of time while retaining inherent mobility. Six reservoir drill in fluids (water and oil based) were proposed by different vendors, and samples thereof and the corresponding screen fluids (if available) were provided. The systematic test program consisted of a sequence of four test phases, where only successful fluids went to the next phase  A description and application of equipment and processes is provided in the complete paper.  Phase I. The first test phase comprised a set of simple screening laboratory tests. The best in class drilling and completion fluids from the study were then tested with regard to formation damage (return permeability tests) Tested qualities included density, particle size distribution, rheology, mobility, settling, emulsion stability, HP/HT filtration and rheology, compatibility, and production screen testing. As detailed in the complete paper, many of the fluids demonstrated acceptable or good performance in many of these aspects; nevertheless, on the basis of observations during Phase I, two out of six fluid systems could already be excluded as unstable for the application (Drilling Fluids 1 and 6)