Fluid Loss Additives Research Articles

Evaluation of the Na-EDTMP/borax system as a non-dispersing, high temperature retarder for oil well cement

For well cementing at temperatures above 120 °C, thermal thinning depicts a major problem, promoting particle sedimentation via decreasing slurry viscosities. This is partly caused by dispersing properties of common high temperature retarder systems and can lead to imperfect zonal isolation, endangering the stability of the wellbore. Counteracting additives tend to start losing their effectiveness at temperatures >140 °C. Other options are often not economically sufficient, increase system complexity or show negative interactions with other additives.Hence, this work presents a comprehensive study on the sodium ethylenediamine tetra(methylene phosphonate) (Na-EDTMP)/borax retarder system, which was found to combine sufficient retardation with low thermal thinning, leading to an enhanced slurry stability at high temperatures. Thickening times (TT's) from 7 to 13 h (increasing with temperature) were achieved from atmospheric pressure and 50 °C up to high pressures and temperatures (HP/HT) of 19.0 kpsi and 200 °C bottom hole circulating temperature (BHCT). Furthermore, On/off-cycle HP/HT consistometer tests at 160 and 190 °C and rheological measurements were performed to examine stability of the slurry's viscosity. Experiments with fluid-loss additives show potential compatibility with other additives.Total retarder dosages of 0.97–2.64 % bwoc (by weight of cement) were applied. Compared to prior literature, higher Na-EDTMP/borax ratios (0.29–0.34 vs. 0.055) were found to improve retarding performance probably by enhancing synergetic effects. The slurries featured a sufficient initial viscosity (<40 Bc) and a constant pumpability (10–25 Bc) during the tests followed by a swift setting and compressive strength (CS) development. Additionally, high slurry stability was shown and compatibility with common fluid-loss additives is probable. Main disadvantage was the relatively high sensitivity of the system, especially at moderate temperatures, requiring exact dosage.Summarizing, the Na-EDTMP/borax retarder system might present a low-complexity opportunity for common high temperature retarders, avoiding thermal thinning while improving slurry stability.

Influence of Rigid Side Chains on the Structural Stability of High-Temperature Resistant Fluid Loss Additives for Oil Well Cements: An Experimental Study and Molecular Simulation

A fluid loss additive (named AAMN) for cementing ultra-deep reservoirs at high temperature (210 °C) was prepared by a free radical copolymerization method using 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamide (AM), acrylic acid (AA), and N-vinyl-2-pyrrolidinone (NVP) as monomers. Filtration tests at 210 °C demonstrated that AAMN reduced the amount of fluid loss by 22% in fresh cement slurry, 23% in 18 wt% NaCl cement slurry, and 16% in 36 wt% NaCl cement slurry compared to AAM (without NVP) when both were added at 6% bwoc ("bwoc" denotes the addition by the weight of the cement). The pore structure was analyzed using the Brenner-Emme-Teller (BET) method and environmental scanning electron microscopy (ESEM), confirming that AAMN could be adsorbed onto the cement particles surfaces, filling the pores and blocking fluid loss channels. The degradation temperatures of the two copolymers were tested by thermogravimetric analysis (TGA-DTGA) and the molecular dynamics behavior of two Amorphous Cell (AC) models (the amorphous structures with randomly arranged Ca2+, Cl−, Na+ and H2O with the AAMN or AAM) built by Materials Studio 7.0 software, were compared: the introduction of five-element NVP side chains didn’t significantly improve the thermal stability of the AAMN relative to the AAM, but resulted in the AAMN molecular chain maintaining a stable geometry at a temperature of 483 K (210 °C). The AAMN also showed more adsorption groups (–SO3 − and –COO−) at the high temperatures, which allowed the AAMN to form a dense "network structure" with Ca2+ and H2O molecules, thus effectively blocking the channels for water molecule loss from the cement slurries.

Effects of Noncrosslinked Polyvinyl Alcohol Fluid Loss Additive on the Compressive Strength and Viscosity of Class G Cement Slurries

Summary Limiting the fluid loss from the cement slurry to the adjacent formation by using additives is essential for maintaining the slurry’s water/cement ratio. The present work focuses on the effect of noncrosslinked polyvinyl alcohol additive (PVOH), a widely used fluid loss additive (FLA), on the compression strength and rheological behavior of Class G cement pastes. Results of the current study show that the PVOH surfactant characteristic and its absorptive mechanism interfere not only with the hydration process but also with the physical properties and compressive strength of cement pastes, such as porosity, permeability, and early age strength, which revealed the importance of using a defoamer when PVOH is present in the mixture. In the absence of a defoamer, the PVOH additive generates foam in the mixed cement paste samples, which results in increased porosity and reduced compressive strength of the hardened cement paste. Moreover, regarding rheology, increasing the PVOH concentration increased the effective viscosity when evaluating flow curves. Therefore, this study demonstrates a systematic method for assessing the possible effects of cement paste additives, such as PVOH and defoamer, providing a physical and mechanical approach rather than just chemical to evaluate additives’ influence on the mixtures. This method should consider different additives in combination with PVOH to test cement paste stability and to obtain specific working recipes.

The Development of Anti-Salt Fluid Loss Additive for Cement-Metakaolin Slurry with Semi-Saturated/Saturated Saline Water: The Application of Maleic Anhydride

Conventional fluid loss additives have difficultly controlling the water loss of cement–metakaolin slurry with semi-saturated brine cement slurry and limiting it to less than 50 mL (30 min)−1. This paper describes the development of an anti-salt fluid loss additive for metakaolin–cement systems. This study adopted the aqueous solution polymerization method; selected four kinds of monomers, namely 2-Acrylamido-2-methylpropane sulfonic acid (AMPS), N,N-Dimethylacrylamide (DMAA), acrylamide (AM), and methyl acrylate (MA); and performed a single-factor experiment on the proportion of monomer, reaction temperature, initiator dosage, and developed fluid loss additive, which has a high salt tolerance and temperature tolerance. This fluid loss additive can resist salt until saturation, and it can control fluid loss in 24 mL·(30 min)−1 when its dosage is 2%. The fluid loss additive can achieve the effect of fluid loss reduction by increasing the filtrate viscosity, forming a flexible elastic adsorption layer via adsorption, and blocking mud cake pores.

Performance comparison and adsorption mechanism analysis of polyanionic and zwitterionic copolymer fluid loss additives for oil-well cement paste: An experimental and computational study

Zwitterionic copolymers, which are synthesized by introducing cationic groups into traditional polyanionic copolymer, are widely used in cementing engineering for complex geological environments for their superior adsorption capacity and antipolyelectrolyte behavior. However, conformational transitions with the temperature and salt of copolymer admixtures remain unclear, thus making it difficult to clarify the adsorption mechanism. In this study, performance comparison and adsorption mechanism analysis of zwitterionic and polyanionic copolymer fluid loss additives (CFLAs) for oil-well cement (OWC) paste were conducted. Results demonstrated that zwitterionic CFLA reduced fluid loss volume and improved compressive strength, despite retarding cement hydration, compared with polyanionic CFLA. Adsorption measurements and molecular simulation revealed that zwitterionic CFLA enhanced its adsorption ability by improving the extension of segment and enhancing electrostatic interaction. The water solubility and adsorption ability of the CFLA decreased due to the shielding effect of multiple counterions gathered near the functional groups and weakening of hydrogen bond.

Modeling Usage of Degradable Fluid-Loss Additive Revamps Fracturing Design

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 210633, “Multimaterial Multiphysics Modeling Coupled With Post-Fracturing Production-Flow Simulations: Revamping Hydraulic Fracturing Design Strategy,” by Abdul Muqtadir Khan, SPE, Vadim Isaev, and Ludmila Belyakova, SPE, Schlumberger. The paper has not been peer reviewed. _ With the aid of a multiphysics simulator, the authors recently presented a novel use of a degradable fluid-loss additive (DFLA) as a fracture geometry additive to reduce the pad volume while achieving the same geometry. In this complete paper, the authors extend advanced slurry flow modeling with production simulation to propose the optimal design strategy for fracturing, which may challenge current treatment-design conventions. A novel work flow was developed, with four coupled working blocks of laboratory, slurry flow modeling, production analysis, and machine learning. The new digital framework proposes solutions for the limitations of current methodology. Introduction Across different generations, multiple fluid additives have been introduced to target specific treatment objectives; one of these that has been available for years, but that has been underused, is fluid-loss additive (FLA). Theoretical and field bases have been presented for its use in the following applications: - Conventional prolific reservoirs to mitigate high fluid loss and create sufficient fracture geometry - Tight gas formations with high tectonic influence to mitigate poroelastic effects and fissure-dependent enhanced leakoff - Unconventional reservoirs to avoid repression during production - Openhole wells to control multiple fracture initiation - Multipad wells to avoid interwell communications and fracture hits - Fracturing treatments aimed at optimizing and reducing crosslinked pad volume Despite these benefits, the primary issue of using an FLA is its potential to damage fracture conductivity and the reservoir. Some developments of nondamaging FLA have been presented but are either operationally complex or difficult to use. This subject requires special attention to investigate damage and production loss through laboratory studies, numerical models, and machine-learning models and define a tailored strategy with DFLA. Digital Framework for Treatment Design The authors present an end-to-end work flow from chemistry development to an automated FLA-assisted fracturing design tailored for a specific reservoir and well. The framework is broadly split into three blocks: laboratory testing, fracture modeling, and production modeling. These blocks can be sensitized together with multiple case runs and a large digital database. This data set then can be subjected to regression and classification algorithms. With enough data built in the toolbox, a fully coupled data- and physics-based forward model can be created that can output the fracture design with DFLA type, concentration, and pad volume with inputs of reservoir properties and pore-throat descriptions. The tool infrastructure is built to allow the model to retrain and update with real field data addition. In the first block, multiple laboratory tests evaluate DFLA performance. The laboratory tests include static and dynamic leakoff tests to evaluate reduction in spurt loss and wall-cake building leakoff coefficient with varying concentrations of DFLA in the fracturing fluid. Additionally, core-flow tests are performed to understand the effect of DFLA on regained permeability and validate the postulation of its nondamaging nature.

A novel preparation of bio-based graphene from oil palm biomass as a fluid loss additive in water-based drilling fluid

The unutilized excess biomass produced by the oil palm sector has become a major source of environmental discussion in Malaysia. Nonetheless, the oil and gas sector has expanded the number of biomass-related projects by implementing zero-carbon net policies. Particularly, graphene has potential applications in the oil and gas industry, including drilling, well logging, desalination, and lubricants. This study introduced a two-step mechanical exfoliation approach to synthesize bio-based graphene (BG) from the lignins of oil palm (Elaeis guineensis) biomass for fluid loss addition in water-based drilling mud (WBM). The BG exfoliation approach is an innovative combination of pyrolysis heat treatment and mechanical exfoliation. This method was developed without chemical exfoliation techniques (Hummers' method) due to its harmful by-products. Several characterization methods were employed, including ultraviolet–visible spectroscopy (UV–Vis), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The sample analyses revealed that the synthesized BG acquired a similar structure to reduced graphene oxide (RGO) due to its comparable C/O ratio. Meanwhile, the efficacy of BG biomass as a fluid loss supplement for WBM was determined when BG was combined with bentonite, sodium carbonate, and water. An American Petroleum Institute (API) filter test and a High-Pressure High-Temperature (HPHT) filter test were performed to assess the fluid loss. Although the API filter test revealed that 0.5 wt% BG possessed the least fluid loss at 10 mL for 30 min, the HPHT filter test indicated that 1.0 wt% BG produced the least fluid loss at 18 mL for 30 min. Therefore, the performance of BG as a drilling mud addition was equivalent to commercial graphene in previous studies. This outcome was demonstrated in the 50% fluid loss reduction and noticeably different surface morphology (less permeability) of the mud cake with a less porous structure and smoother surface.

Modification and Application of Materials for Strong Inhibitory Drilling Fluid

Due to the strong inhibition of drilling fluid, many polymer fluid loss additives can not play their role. Therefore, it is necessary to develop some water loss reducing materials that can withstand the strong inhibition environment. In this paper, the surface of asbestos fiber was modified and treated by indoor experiments. The physical and chemical properties of the obtained drilling fluid treatment samples were evaluated to optimize the appropriate amount of reagents used for surface treatment of asbestos. Subsequently, the drilling fluid performance of the obtained treatment agent samples were evaluated at different temperatures to analyze the effect of temperature on the drilling fluid performance. The surface of asbestos fiber was modified by adsorbed cationic surfactant CTAC which better solved the problem of entanglement of asbestos fiber in drilling fluid. The mechanism of the action of the surface of asbestos fiber was analyzed by scanning electron microscope observation experiments. Subsequently, different amounts of modified asbestos fiber was added to the drilling fluid and the performance of drilling fluid was evaluated at different temperatures. The experimental results showed that the modified asbestos fiber reduced the filtration loss of drilling fluid and still maintained good filtration loss reduction effect at 200°C.

Modification and Application of Materials for Strong Inhibitory Drilling Fluid

Due to the strong inhibition of drilling fluid, many polymer fluid loss additives can not play their role. Therefore, it is necessary to develop some water loss reducing materials that can withstand the strong inhibition environment. In this paper, the surface of asbestos fiber was modified and treated by indoor experiments. The physical and chemical properties of the obtained drilling fluid treatment samples were evaluated to optimize the appropriate amount of reagents used for surface treatment of asbestos. Subsequently, the drilling fluid performance of the obtained treatment agent samples were evaluated at different temperatures to analyze the effect of temperature on the drilling fluid performance. The surface of asbestos fiber was modified by adsorbed cationic surfactant CTAC which better solved the problem of entanglement of asbestos fiber in drilling fluid. The mechanism of the action of the surface of asbestos fiber was analyzed by scanning electron microscope observation experiments. Subsequently, different amounts of modified asbestos fiber was added to the drilling fluid and the performance of drilling fluid was evaluated at different temperatures. The experimental results showed that the modified asbestos fiber reduced the filtration loss of drilling fluid and still maintained good filtration loss reduction effect at 200°C.

Evaluation of the suitability of Pleurotus as a fluid loss control agent using the chemical structural properties approach

One of the main functions of the drilling fluid is to prevent filtrate from entering the formation by exhibiting good fluid loss properties during oil and gas drilling operations by sealing off the walls of the wellbore. Pleurotus is a type of edible mushroom that has been discovered by researchers to play the role of fluid loss additives in the mud system. The Pleurotus sample was processed as per the API standard and measured accordingly using laboratory measurements such as Scanning Electron Microscope Energy Dispersive X-ray Spectroscopy (SEM-EDS) for characterization, the X-Ray diffraction (XRD) methods used by scanning the sample to determine the chemical structure, name, and physicochemical properties by matching the results obtained with a different library, such as the NIST and PubChem. The Fourier Transform Infrared Spectrometer-FTIR 8600S helped to discover some of the functional groups which then confirmed the results and the matching of the XRD. The key chemical composition of Pleurotus are Chitin, glucans, and glycoproteins and their functional groups are amine (NH) and hydroxyl (R-OH), its high fiber and cellulose contents from chitin and glucans are the main constituents in the fluid loss control characteristics for its effectiveness. The position of the carbon-carbon, nitrogen-hydrogen, and hydrogen-oxygen indicating the point of the double bond was confirmed from the FTIR. The result of the sample was matched and found to be Psilocin which gave the structures to be more amorphous since they are more organic materials.

Biopolymeric formulations for filtrate control applications in water-based drilling muds: A review

The forthcoming future of environmental protection mandates the utilization of naturally abundant, biodegradable, sustainable and ecofriendly materials for a wide variety of applications. Fluid loss behavior is considered the most severe problem in oil and gas well drilling operations. Because several other issues are associated with it. As a working way out, viscosifiers and fluid loss additives are introduced to the mud for rheology and filtration characteristics improvements, respectively. Polymers and starches are commonly added to base fluid to increase viscosity and reduce fluid loss of a mud. In this paper, the utilization of biopolymers used in the drilling fluid industry for filtrate reduction has been addressed. This review further emphasizes on the recent developments in native and modified starches utilization in drilling fluids extracted from various sources and the present research gaps for future developments. The utilization of biopolymers as potential additive in nondamaging water-based muds have been addressed to reduce the impacts of mud filtrate in the exposed formations. Moreover, various factors that influence the effectiveness of biopolymers and the utilization of such polymers in different muds are also discussed. The filtration characteristics in terms of filtrate volume and filtercake thickness generally showed improvements by using biopolymers. Filtercakes generated from starch-containing muds have been found to be thinner and more compact, resulting in reduced formation damage due to lower mud particle penetration.

Poly(ionic liquids) based on β-cyclodextrin as fluid loss additive in water-based drilling fluids

Well wall collapse due to massive fluid in water-based drilling fluids (WDFs) intrusion into the reservoir is an urgent issue during oil drilling. In this study, we synthesized the poly(ionic liquids) (PILs) based on β-cyclodextrin and investigated its novel application as fluid loss additive in WDFs. American Petroleum Institute standard filtration tests showed that the PILs exhibited excellent filtration control performance even after hot rolling at 180 °C for 16 h compared to commercial fluid loss additives (Driscal D, PAC-Lv, CMC). Specifically, the fluid loss volumes of Driscal D/WDFs, PAC-Lv/WDFs and CMC/WDFs were 10.4 mL, 12.4 mL and 14.8 mL respectively after hot roll at 180 °C for 16 h, however, the fluid loss of PILs/WDFs was only 2.8 mL. The extremely low filtration rate, thickness and permeability of the PILs/WDFs mud cake resulted in exceptionally low fluid loss volume. Additionally, the mechanism of PILs controlling fluid loss in WDFs was revealed by bentonite particle size measurement and Zeta potential measurement. This work demonstrates that PILs have the promising application as an efficient fluid loss additive in WDFs due to the outstanding filtration loss reduction behavior.

Analysis of the Weight Loss of High Temperature Cement Slurry

The weight loss of cement slurry is the main cause of early annular air channeling and accurate experimental evaluation of the law of loss change is the key to achieve compression stability and prevent this undesired phenomenon. Typically, tests on the pressure loss of cement slurry are carried out for temperature smaller than 120°C, and this condition cannot simulate effectively the situation occurring in high temperature wells. For this reason, in this study a series of experimental tests have been conducted considering a larger range of temperatures, different retarders and fluid loss additives. The results show that with an increase in the temperature, the weight loss curve of cement slurry changes from a “two-stage” to a “three-stage” behavior, and the risk of channeling increases accordingly. On increasing the amount of retarder and fluid loss additive, the transition time of cement slurry displays a non-monotonic behavior (it decreases first and then increases). It is found that the optimized retarder and fluid loss additive dosage are 0.2% and 2.5%, respectively.

Assessment of the Performances of Carboxylic Acid Monomers as Fluid Loss Additives for Oil-Well Cement

The application of polycarboxylic acid as a fluid loss additive for cement (i.e., a substance specifically designed to lower the volume of filtrate that passes through the cement) can prolong the thickening time of cement slurries. Given the lack of data about the effects of carboxylic acid monomers as possible components for the additives traditionally used for oil-well cement, in this study different cases are experimentally investigated considering different types of these substances, concentrations, temperatures, and magnesium ion contamination. The results demonstrate that itaconic acid has a strong retarding side effect, while maleic and acrylic acids have similar influences on the thickening time of the cement slurry. The rheological properties of the cement slurry tend to deteriorate when the carboxylic acid monomer content in the fluid loss additive is increased to 40%. If the temperature exceeds 80°C, there is a significant decrease in the related impact on the thickening duration. With an increase in the intrusion of magnesium ions to >0.5%, both the rheological properties of the cement slurry and the thickening time are affected in a negative way.

Comprehensive investigation and mechanisms of drilling waste sludge dewaterability by Fe(Ⅱ)/persulfate pretreatment

The drilling waste sludge mainly sourced oil well cement slurry with fluid loss additives. The fluid loss additives make the drilling waste sludge has strong water holding capacity. The preliminary difficulty of reduction of drilling waste sludge was dewatering. Fe(Ⅱ)/persulfate pretreatment was reported to improve dewaterability and reduce organic matter in sludge. Herein, we systematically investigated Fe(Ⅱ)/persulfate pretreatment on improving the dewaterability of drilling waste sludge and revealed the involved mechanism. The experimental results showed the Fe(Ⅱ)/persulfate pretreatment decreased the water content (WC) and specific resistance to filtration (SRF) of sludge filter cake to 29.73% and 79.46% respectively with 16 mg/g DS (dry solid) Fe(Ⅱ) and 12 mg/g DS persulfate. In addition, the dewatering time was decreased by 80.38%. The correlation analysis results indicated that these characteristics interactions (sludge VSS solubilization, particle size, Zeta potential, viscosity and dewatering) significantly influenced the dewatering of drilling waste sludge. Mechanism investigation revealed that high VSS content in sludge had strong water affinity capacity and negative Zeta potential, which inhibited the dewaterability and aggregation. When Fe(Ⅱ)/persulfate pretreatment decomposed sludge flocs and oxidized organic matter, the bound water adsorbed was released. The cations of Fe2+ and Fe3+ compressed the double electric layer alleviating the electronegativity and aggregated the sludge particles. Consequently, the aggregated drilling waste sludge reinforced the hydrophobicity and porous structure, which availed to drain bound water out and improve the deep dewatering. This work provides possible strategy supports for drilling waste sludge dewatering in the future.

Experimental Study of Sugarcane Bagasse Ash and Corn Starch as Fluid Loss Additives in Oil-Based Drilling Mud

Fluid loss is one of the biggest problems faced by the drilling engineers; the drilling fluids invades in the formation resulting in the fluid loss, which increases the overall cost of the drilling. The objective of this study is to use biodegradable natural ingredients as fluid loss additives in oil-based mud as the industrial based polymers which are normally used as fluid loss agents are highly expensive. In this study, corn starch and sugarcane bagasse ash were used at 1, 3, 5, and 7% wt./wt. separately as fluid loss additive in Oil-based mud. The drilling mud mixed with 1% of SCBA yielded the best result for fluid loss. Similarly, corn starch at 1% wt./wt. exhibited the best fluid loss characteristics. However, their effect on other mud properties was; plastic viscosity, apparent viscosity, yield point, and gel strength increased with increasing the concentration whereas, they have no or little effect on pH and mud weight.

Study on the working mechanism of fluid loss additive for chlorination titanium blast furnace slag

The chlorination titanium blast furnace slag belongs to industrial waste, but after grinding, they can be used to prepare cementing fluids to realize the secondary utilization of solid waste resources. As a common additive, fluid loss additives are mostly used in oil well cement systems, and there is still a lot of room for development when applied to chlorination titanium blast furnace slag systems. In this paper, the AMPS/DN-1/DMC/AA tetramer fluid loss additive was synthesized by free radical polymerization and named as ADDA. After testing its adsorption, hydration and plugging experiments, the TOC results showed that with the increase of ADDA, the organic carbon absorption increased from 5.68 mg/L to 34.59 mg/L; the BET results showed that, with the increase of ADDA, the specific surface area decreased from 15.3976 m3/g to 8.4157 m3/g. Combined with the microscopic morphology and other tests, it is shown that ADDA can effectively adsorb slag particles due to the electrostatic interaction of the sulfonic and carboxyl group in its molecular structure and the steric effect of the quaternary amine group. In addition, ADDA can promote the hydration reaction of the slag and entangle with the hydration products to form a complex network structure, thereby changing the filter cake structure to produce a dense and uniform filter cake; Polymer macromolecules can also effectively block the "gap" and "holes" in the structure, greatly reducing the flow path of free water, thereby realizing the control of water loss.

Novel Starch Composite Fluid Loss Additives and Their Applications in Environmentally Friendly Water-Based Drilling Fluids

With increasing intensified environmental pressure and a complex drilling environment, developing high-performance fluid loss additives with environmental acceptability is becoming a research focus...

Experimental study on water-based drilling fluid for horizontal wells

ABSTRACT High-yield shale gas flow has been discovered in the Cambrian Shuijingtuo group shale (the Shuijingtuo shale) of the first shale gas well of Yichang, West Hubei, China. However, there are very few papers or reports involving high-performance water-based drilling fluid for the Shuijingtuo shale. X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) tests were conducted on the outcrop of the Shuijingtuo shale samples collected from Zigui County, West Hubei. Then, the screening experiments on mud-making materials, salt additives, nanoparticles, fluid loss additives, mixed metal hydroxides (MMH), and surfactants were carried out. A high-performance water-based drilling fluid for the Shuijingtuo shale (the SWDF drilling fluid) was proposed based on physical plugging by nanoparticles, electrical property inhibition, and wettability control theory. Finally, comprehensive appraisals on rheology, filtration, lubricity, temperature resistance, inhibition, anti-pollution capability, and expense of the SWDF drilling fluid were accomplished. XRD results showed that the Shuijingtuo shale samples had 55%~67% brittle minerals. Clay minerals were mainly illite (13%~27%), and no montmorillonite was observed, which indicated that the Shuijingtuo shale was a weak-expansive rock. SEM analysis results show that pore and micro-cracks on the surface of the Shuijingtuo shale could provide natural channels for the invasion of drilling fluid. Nanomaterials were found to reduce the fluid loss of drilling fluid and thermal stability of the nano-silica dispersion was better. As a whole, the SWDF drilling fluid had suitable viscosity and gel strength, a low API fluid loss of 7.2 mL, a lubricity coefficient of 0.21, temperature-resistance capability up to 120°C, and good inhibition to shale hydration. In addition, it had excellent resistance capability to inorganic salts (NaCl, MgCl2, and CaCl2) and low-yield mud-making materials (simulated cuttings). Also, the cost of the SWDF drilling fluid was competitive compared to common oil-based drilling fluids. As a consequence, the SWDF drilling fluid can meet the requirements of drilling horizontal wells in the Shuijingtuo shale of West Hubei, China.

A novel zwitterionic quaternary copolymer as a fluid-loss additive for water-based drilling fluids

ABSTRACT Wellbore instability and formation collapse are crucial issues in the process of well excavation in the oil industry under extreme high temperature conditions. A novel zwitterionic quaternary copolymer (PDANV) of 4-vinylpyridine (VP), N, N-dimethylacrylamide (DMAA), 2-acrylamido-2-methylpropane sulfonic acid, N-vinylcaprolactam (NVCL) was synthesized in aqueous solution by free radical copolymerization reaction. The structure of PDANV was characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (1 H NMR), and the results indicated that ideal product are obtained. Thermal stability of PDANV was revealed by thermogravimetric analysis (TGA) and result showed that thermal degradation of PDANV mainly happened over 301°C. Simultaneously, PDANV was prepared to further evaluate its effect on rheological and filtration properties of water-based drilling fluids (WBDFs). The results showed that the fluid loss (FLAPI) of PDANV/WBDFs was only 3.4 mL, 6.0 mL before and after hot rolling at 260°C for 16 h, respectively. Compared with the 19.2% and 57.9% reduction of traditional fluid-loss additives CMC and Driscal, the fluid-loss reduction rate of PDANV/WBDFs was 87.5% in ultra-high temperature environment. Additionally, PDANV performed satisfactorily with great properties in WBDFs even at high concentration of salts and calcium. Therefore, it can be used for applications where the PDANV is subjected to certain harsh environments, such as extreme salinity and ultra-high temperature conditions.