Cake Removal Research Articles

Evaluation of Biosurfactants to Preflush for Offshore Wells.

With the improvement of environmental protection requirements in offshore oil and gas exploration, there is a great demand to find environmentally friendly surfactants for cementing preflush fluids. In the present paper, the application potential of three biosurfactants of rhamnolipid, lipopeptide, and sophorolipid in the preflush fluid was evaluated through a series of experiments. The experiments studied the interfacial tension (IFT) of the biosurfactants, resistance to temperature, salt resistance (sodium chloride and sea salt), and the influences of the studied biosurfactants on the rheological compatibility and capabilities to convert the wettability of the formation from oil-wet to water-wet, mud cake removal efficiency, and to improve the interfacial bonding properties of the preflush fluid. The results showed that rhamnolipid, lipopeptide, and sophorolipid exhibited excellent surface activities in high-temperature and sodium chloride (NaCl) environments. When exposed to sea salt, lipopeptides lost their function due to agglomeration, while rhamnolipids and sophorolipids maintained structural stabilities and high surface activities. When rhamnolipid was mixed with sophorolipid in a ratio of 2:1 at the same concentration, the combined biosurfactant had the best surface activity among the studied surfactants. The combined biosurfactant not only had good rheological compatibility with the drilling fluid and cement slurry but also showed excellent properties in the removal of mud cake. In addition, the effect of the removal of the mud cake was verified by the gas channeling experiment. The experimental results show that the presence of mud cake can reduce the bonding strength. When rhamnolipid was mixed with sophorolipid in a ratio of 2:1 at the same concentration, the removal efficiency of mud cake was the highest, and the interfacial bonding property of the cement sheath can be improved.

Evaluation of formation damage and filter cake removal with a new LPM drilling fluid additive

This study evaluates the LPM-FBR drilling fluid additive's performance in minimizing formation damage and facilitating filter cake removal in fractured and high-permeability cores. Using a Formation Damage System Apparatus, two experimental studies were conducted to address the challenge of balancing fluid loss control and formation damage mitigation in fractured reservoirs. The first study, comparing a base saltwater mud with and without LPM-FBR on a 1231 mD fractured sandstone core, showed that LPM-FBR significantly enhanced fluid loss control. It withstood 552 psi overbalance pressure with minimal fluid loss (85.6 mL over 6 h), effectively sealing fractures. However, it reduced return permeability from 1500 to 47.8 mD. The second study, using a 2000 mD fractured core, demonstrated LPM-FBR's effectiveness in limiting filtrate invasion to 5.7 mL over 4 h at 600 psi overbalance. Subsequent cleaning with caustic soda proved ineffective, severely impairing return permeability to 19–28 mD. A breaker solution with a high flow rate of water flushing showed more promise in filter cake removal. This research highlights the trade-offs between fluid loss control and formation damage when using LPM-FBR muds. While excelling in minimizing fluid losses under high overbalance conditions, the additive poses challenges in post-drilling permeability restoration. These findings underscore the need for comprehensive removal procedures to mitigate long-term productivity impairment in fractured reservoirs, contributing valuable insights for optimizing drilling fluid design and post-drilling cleanup strategies.

Optimizing hematite filter cake treatment using reducing agents

In drilling operations, the formation of a filter cake is crucial for well stability, but its removal post-drilling is essential to restore rock formation productivity. This study focuses on hematite-based filter cakes and investigates factors influencing their solubility and removal, addressing a significant knowledge gap in the field. The research methodology involves examining the effects of various factors, including types and concentrations of reducing agents, temperature, particle size, and treatment duration, on the dissolution process. Notably, Nuclear Magnetic Resonance (NMR) tests are employed to assess the treatment's impact on core porosity. Among the diverse reducing agents examined, ferrous chloride emerges as the optimal choice for effectively enhancing hematite solubility. Particularly, a composite solution of ferrous chloride (10 wt.%) and hydrochloric acid (6 wt.%), was highly efficient demonstrated by exhibiting rapid solubilization of hematite filter cakes. A removal efficiency of approximately 99%, with a parallel enhancement in core permeability was achieved. NMR tests reveal the treatment's success in reinstating the porosity system, which had undergone reduction due to drilling fluid particles. Crucially, the solution exhibits a considerably lower corrosion rate than concentrated hydrochloric acid, highlighting its potential to mitigate environmental concerns while ensuring efficient filter cake removal. The findings of this research provide valuable insights into optimizing post-drilling operations, balancing environmental sustainability and operational efficiency. The identified composite solution offers a promising approach to efficient filter cake removal while mitigating environmental concerns associated with corrosion. Overall, this study contributes to advancing the understanding and practice of well productivity enhancement in the oil and gas industry.

Influence of precoating on the regeneration efficiency of filtration inorganic membranes

AbstractInorganic membranes are used to effectively capture particulate matter in dust without causing secondary pollution. However, fine dust particles accumulate on the surface and penetrate the structure of inorganic membranes, thereby degrading their performance. This study investigated the influence of the precoating of inorganic membranes with needle‐shaped wollastonite particles on their regeneration efficiency. The filter‐cake‐curing technique was employed, and the results were obtained by characterization methods, including scanning electron microscopy and energy‐dispersive spectroscopy. The mechanism for controlling membrane fouling was examined based on the quantity and depth of particle penetration to the filtration medium and pore structure of the filter cake. The results demonstrated that precoating can prevent fine particles from penetrating the membrane pores, thereby alleviating pore blocking in inorganic membranes. Furthermore, this increased the porosity and decreased the fractal dimension of the pore in the cake, thereby reducing the structural complexity and resistance during cake removal. The regeneration efficiency of the inorganic membrane increased from 59.4% without a precoating to 94.1% when wollastonite particles with an aspect ratio of 10 were used for precoating.

Preparation and Properties of Reversible Emulsion Drilling Fluid Stabilized by Modified Nanocrystalline Cellulose.

Reversible emulsion drilling fluids can concentrate the advantages of water-based drilling fluids and oil-based drilling fluids. Most of the existing reversible emulsion drilling fluid systems are surfactant-based emulsifier systems, which have the disadvantage of poor stability. However, the use of modified nanoparticles as emulsifiers can significantly enhance the stability of reversible emulsion drilling fluids, but ordinary nanoparticles have the disadvantages of high cost and easily causing environmental pollution. In order to solve the shortcomings of the existing reversible emulsion drilling fluid system, the modified nanocrystalline cellulose was considered to be used as an emulsifier to prepare reversible emulsion drilling fluid. After research, the modified nanocrystalline cellulose NWX-3 can be used to prepare reversible emulsions, and on this basis, reversible emulsion drilling fluids can be constructed. Compared with the reversible emulsion drilling fluid stabilized by HRW-DMOB (1.3 vol.% emulsifier), the reversible emulsion drilling fluid stabilized by the emulsifier NWX-3 maintained a good reversible phase performance, filter cake removal, and oily drill cuttings treatment performance with less reuse of emulsifier (0.8 vol.%). In terms of temperature resistance (150 °C) and stability (1000 V < W/O emulsion demulsification voltage), it is significantly better than that of the surfactant system (temperature resistance 120 °C, 600 V < W/O emulsion demulsification voltage < 650 V). The damage of reservoir permeability of different types of drilling fluids was compared by physical simulation, and the damage order of core gas permeability was clarified: water-based drilling fluid > reversible emulsion drilling fluid > oil-based drilling fluid. Furthermore, the NMR states of different types of drilling fluids were compared as working fluids, and the main cause of core permeability damage was the retention of intrusive fluids in the core.

Construction and Evaluation of a Degradable Drilling Fluid for Underground Coalbed Methane Extraction Boreholes.

Gas drainage with bedding boreholes is an efficient method for preventing gas and achieving coal and gas comining in underground mining engineering. An underground pressurized drilling method is proposed to maintain the borehole stability. However, the presence of natural fractures in coal seams poses challenges during pressurized drilling. Therefore, it is crucial to establish a low-leadage degradable drilling fluid system that minimizes coal seam damage. In this study, a degradable drilling fluid system was developed based on the characteristics of coal seams. The performance and influencing factors of the drilling fluid and the degrading capability of cellulase were examined. Moreover, the damage of the drilling fluid on fractured coal seams was investigated using core flow test methods. The results showed that additives significantly improved the rheology, filtration, and inhibition of the drilling fluid. The drilling fluid system exhibited excellent stability, rheological properties, low filtration, and sealing performance in coal seam environments. However, drilling fluid invasion and mud cake blockage negatively affected gas flow in fractured coal seams, and a higher content of filtrate reducer hindered the recovery of the gas flow rate. Cellulase was used to degrade polymers and alleviate the challenge of mud cake removal after drilling. Research on the influencing factors of cellulase indicates that the degradation efficiency of cellulase enzymes is influenced by the temperature, pH, salinity, and solid-phase content. For polluted coal samples, the gas flow rate significantly recovered after treatment with a cellulase solution. This study provides insights into a degradable drilling fluid system that can enhance underground pressurized drilling methods and minimize reservoir damage.

Creation of expanded diameter gravel wells in unconsolidated for-mations for High-Temperature Aquifer Thermal Energy Storage Sys-tems: Theoretical and numerical evaluation of borehole stability

High-Temperature Aquifer Thermal Energy Storage (HT-ATES) systems have the potential to cost-effectively store large volumes of thermal energy, bridging the supply-demand gap for variable renewable heat sources, such as solar thermal or power-2-heat conversion [3, 4]. These systems involve the injection and extraction of heated and cooled groundwater in aquifers via tube wells [11]. A HT-ATES system will be showcased at TU Delft, which involves the use of an Expanded Diameter Gravel Well (EDGW) to increase well capacity and reduce mechanical clogging compared to conventional wells [9]. This has the potential to reduce the number of wells needed and lower the costs of the HT-ATES system.&#x0D; An EDGW has previously been constructed at depth in unconsolidated formations using a jetting technique for borehole expansion [8]. This well (expanded 2.6 fold from 600 mm to 1570 mm diameter) was taken into routine operation for drinking water production. A second expanded borehole (expanded 4.1 fold from 600 to 2460 mm diameter) collapsed upon testing the enhanced removal of the filter cake before it could be completed as EDGW. The missing explanation for the collapse of the second well highlights a knowledge gap regarding the stability of an expanded diameter borehole in unconsolidated formations. To prevent collapse of future expanded boreholes and to better manage the drilling process, this study aims to investigate the effects of an enlarged diameter on well stability through a theoretical analysis.&#x0D; The stability of the EDGW borehole is evaluated in two ways, see Figure 1 for a schematic of the workflow. Firstly, the effects of an enlarged diameter on the stability of the well are evaluated analytically using a poroelastic framework [1, 2, 7]. Different conditions are taken into account regarding the stress state, mud pressure, and hydraulic conductivity of the aquifer. Secondly, field test conditions for the anticipated EDGW in the HT-ATES system are simulated numerically using the two and three-dimensional finite element software. The EDGW to be built in Delft, will be constructed within the Maassluis formation. The target aquifer is located at a depth of 120 – 182 m and is mainly composed of sandy units [5]. The simulation is divided into an initial, drilling, and open borehole (seepage) stage [6, 10]:&#x0D; &#x0D; During the initial stage, in-situ stresses and pore pressures are applied.&#x0D; The well bore volume will be removed during the drilling stage, resulting in a stress state that is no longer in equilibrium, and a mud pressure is applied to the borehole wall.&#x0D; For the open borehole prior to backfilling stage, the effect of time-dependent fluid flow due to mud losses is evaluated on well stability.&#x0D; &#x0D; During the open borehole stage, both situations with and without the presence of a filter cake (varying in thickness and hydraulic permeability) will be evaluated. Furthermore, the effect of the presence of thin clay/silt layers on the stability problem will also be taken into account, where special attention is paid to the roof of the well.&#x0D; The final results of this study are presented in the form of critical conditions regarding stress state, required mud pressure, and hydraulic conductivity for enlarged diameter boreholes in unconsolidated formations. Additionally, a design for the EDGW field test as part of the HT-ATES system in Delft is proposed, taking into account uncertainties such as the in-situ stress state and strength parameters of the formation.

Ultrasonic cleaning in the membrane process: From phenomenon to mechanism and mathematical model

An inhibition effect of cavitation bubbles on cake removal was observed for the first time in the ultrasonic cleaning process. Then, a mathematical model simultaneously considering inhibition effect, bubble dynamics, and actual nonuniform cake structure was established based on force analysis. The result showed that model could precisely predict the flux recovery rate (FRR) (R2 > 0.97). Furthermore, the model was used to determine the theoretical cleaning efficiencies (FRR*) under different conditions: FRR* increased with power whereas decreased with frequency, the highest value was 91.26%(1.0 W/cm2&20 kHz). Besides, a comparison between FRR* and FRR indicated that a duration of 120 s was enough in ultrasonic cleaning. Critical duration determined by the half-life period method successfully evaluated the significant jump in FRR. Additionally, different foulants and multi-cycle experiments were carried out to validate the application of the model and energy conservation (60–70%) of periodical ultrasonic cleaning. This study provided significant insights into industrial ultrasonic cleaning process.

Understanding the complexity of secondary formation damage: Mechanism and detection strategies during filter cake removal process

Formation damage has a negative impact on the productivity of a well. Hence, its mechanism needs to be well understood to be able to mitigate it. Secondary damage is a form of formation damage that occurs during the removal process of barite filter cake layer but has received less attention. This study focuses on examining the secondary damage that occurs during the removal process of barite filter cake layer using chelating agents. Ethylenediaminetetraacetic acid (EDTA) with a concentration of 20% was employed as an effective treatment solution for removing the barite filter cake. EDTA was prepared as a pure solution (referred to as EDTA-K) and saturated with barium (referred to as EDTA-Ba) to simulate the solution state after the completion of filter cake removal. Experiments were conducted using different rock samples, including a sandstone and a carbonate core, to investigate the interaction between the chelating agent and the formation through a core flooding system. Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) were applied to evaluate the alterations in the inner pore structure, and pore size distribution due to the EDTA reactivity. Furthermore, the changes in rock samples’ permeability were examined. Results showed that the reactivity of EDTA varies depending on the rock type and the presence of specific ions. EDTA exhibited limited reactivity with sandstone samples because of its weak ability to react with the silicate matrix and limited content of clay minerals containing Al3+ and Mg2+, highlighting a lower potential for secondary formation. In contrast, carbonate samples demonstrated higher reactivity with EDTA, leading to enhanced permeability. However, the precipitation of barium within the pores of carbonate rocks was observed, which can be considered as a significant level of secondary formation damage. Ab initio calculations supported the experimental findings by demonstrating the binding ability of EDTA with different ions.

Corrosion behavior and mechanism of P110 casing steel in alkaline-activated persulfate-based preflush fluid

Alkaline activated persulfate based preflush fluid has promising potential on mud cake removal in oil and gas well. However, the corrosion on casing steel is rarely investigated. In this work, the corrosion rate of alkaline activated potassium persulfate (KPS) solution on P110 steel was investigated by weight-loss corrosion experiment. The corrosion behavior, changes on surface morphology and corrosion products was characterized by using potentiodynamic polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The results show that the corrosion rate of P110 steel changes from 0.027 mm/y to 4.076 mm/y with the increase of KPS concentration from 10 mM to 40 mM under 90 °C. But the corrosion rate decreases obviously with the increase of NaOH concentration from 60 to 160 mM with a high KPS concentration (40 mM). Besides, The corrosion degree tends to be stable after 50 °C, which indicates the corrosion rate is less affected by temperature. The corrosion is dominated by charge transfer process through the synergistic effect of acid and oxidation. Corrosion products are mainly composed of Fe2O3, Fe3O4, and FeO(OH). The result is conducive to optimize the preflush fluid and the selection of corrosion inhibitors in the future work.

High-Temperature Water-Based Drilling Fluid Accesses Depleted Deepwater Reserves

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 207825, “First Use of Novel High-Temperature Water-Based Reservoir Drilling Fluid To Access Depleted Deepwater Reserves,” by Alexandra C. Morrison, Conan King, SPE, and Kevin Rodrigue, Halliburton. The paper has not been peer reviewed. _ A combination of divalent base brine and high wellbore temperature presents significant challenges for high-density aqueous reservoir drilling fluids. Such systems traditionally use biopolymers as viscosifiers; however, they are subject to degradation at elevated temperatures. Nonaqueous drilling fluids are thermally stable, but complete removal of the filter cake is challenging, which can lead to formation damage. The complete paper describes the qualification and first deepwater drilling application of an aqueous reservoir drilling fluid at temperatures greater than 320°F. Introduction The laboratory development and scale-up yard trials of the high-temperature divalent brine-based reservoir drilling fluid (HT-RDF) and solids-free screen running fluid (SF-SRF) systems used for this well took several years. Specific rheology and fluid-loss targets were set and met during the design phase, and, in conjunction with hydraulic modeling, software simulations demonstrated that equivalent circulating densities (ECDs) would be acceptable based on well-construction plans. The HT-RDF showed excellent thermal stability in static age tests, which was crucial because of the plans for openhole logging of the production zone once total depth was reached. Screen plugging was identified early in the project as a key risk; the most-suitable mitigation for this was to engineer a completely solids-free fluid in which to install the sand screens. The resulting SF-SRF was designed to provide fluid-loss control and wellbore stability in case filter cake was stripped from the formation face during the screen run. Finally, given the focus on production maximization, the fluids underwent rigorous formation-damage tests, ultimately showing that a return permeability of greater than 60% was possible with the inclusion of an acid breaker to assist filter-cake dissolution.

CFD Validation for Assessing the Repercussions of Filter Cake Breakers; EDTA and SiO2 on Filter Cake Return Permeability

ABSTRACT Drill-in-fluids create what are known as filter cakes. Filter cakes, in some cases, lead to well abandonment because they prevent hydrocarbons from flowing freely from the formation into the wellbore. Cake removal is essential to avoid formation damage. A previous study on filter cake breakers was considered for computational fluid dynamic (CFD) validation. Matlab-CFD and Navier-Stokes equations aimed at predicting and validating visual, multiphase flow under finite element analysis (FEA). The interactions of separate chemical breakers and drill-in-fluid such as ethylenediaminetetraacetic acid (EDTA), silica-nanoparticle (SiO2), and biodegradable synthetic-based mud drill-in-fluid (BSBMDIF) were monitored under a particle size distribution, viscosity, density, and pressure. Predicting return permeability of filter cake was considered under a simple filtration process. The particles’ deposition created pore spaces between them; barite 74 μm, nano-silica 150 nm, and EDTA 10 μm generally closed up the pores of the filtration medium. Under extreme drilling conditions, barite formed thicker regions, and EDTA chemical properties easily disjointed these particles, while SiO2 entirely did not. The experimented results of (EDTA) and SiO2 for return permeability were in full force agreeable with the 2D simulation. A hybrid computational analysis considering CFD under discrete element analysis and neural network can be employed for further research validations.

Maximizing well productivity by using filter cake breaker for synthetic-based mud drill-in fluid (SBMDIF) system

• Formation damage has a significant impact on the overall performance. • An effective filter cake breaker selection is critical to minimize formation damage. • The straightforward reaction of meso‑surfactant and nano-surfactant filter cake breakers with barite. • Surfactant-based filter cake breaker was more efficient in removing synthetic-based drilling mud. Formation damage has a significant impact on the overall performance of the well productivity. Removal of filter cake which is deemed to be the main strategy of formation damage remediation is crucial in open hole completion with pre-slotted liner or stand-alone screen (SAS) as a mean of sand control. Without proper planning, inefficient filter cake removal can lead to tremendous consequences since filter cake can plug the sand control component. Making the condition worse, sand control component is susceptible to plugging. This highlights the importance of selecting an effective filter cake breaker that can successfully remove the filter cake through dissolution of the main solids that constitute the major portions of the filter cake which could be the weighting material, barite, or calcium carbonate. Besides that, a proper understanding of the mechanism of the filter cake breaker chemical would be very beneficial to comprehend the filter cake breaker efficiency. The laboratory study attempted to emulate the reservoir condition. Regained permeability testing using High Pressure High Temperature (HPHT) Filter Press aimed to test the ability of several commercial filter cake breakers in removing synthetic-based-mud drill-in-fluids (SBMDIF). Chelating-based filter cake breaker, meso‑surfactant-based filter cake breaker and nano-surfactant-based filter cake breaker were the samples to be tested in the laboratory work. The condition of the filter cake after being soaked statically was visually interpreted and the regain permeability was recorded. The mechanism of each filter cake breaker to remove the SBMDIF filter cake was also examined. Based on the experimental study, meso‑surfactant-based filter cake breaker was found to be more effective to remove SBMDIF filter cake compared to chelating-based filter cake breaker and nano-surfactant-based filter cake breaker.

A multi-functional rinsing model based on cake properties for predicting rinsing efficiency and calculating energy consumption in MBR

The model establishment is of great significance to realize the automatic operation of membrane bioreactor (MBR). In this study, a multi-functional rinsing model based on the variation of cake properties was established to predict the instantaneous fouling resistance/rinsing efficiency (η) of 0.1 μm PAN membranes fouled with activated sludge suspension and calculate the energy consumption (W) for cake removal. The results showed that the model predictions had good agreements with experimental data (R2>0.960). Meanwhile, the cake thickness (L)/porosity (εc) decreased while the specific cake resistance (r) increased in the ringing process. And the cake with smaller εc and larger r was more difficult to remove. In addition, the transition points of W (uw) and η (uη) were determined (uw < uη). And the variation trend of η and W could be divided into three stages: (i) η increased rapidly while W increased slowly before uw; (ii) η increased slowly while W increased rapidly in the range from uw to uη; (iii) η increased slightly while W increased more rapidly after uη. The suitable cross-flow velocity range (uw < u < uη) and the suitable working region were determined after weighing W and η, which can be used to select optimal rinsing conditions in the actual MBR.

Removal of Hematite Water-Based Filter Cake Using Hydrochloric Acid

The filter cake layer, which is essential to reduce the fluid invasion to the drilled formation, has been reported to be composed mainly of the weighting materials. The complete removal of this layer is recommended to restore the rock permeability. Hematite is one material that is used to create the filter cake. However, the cleanup of hematite-based filter cake has not been studied thoroughly. The objective of the work presented in this paper is to investigate the removal of hematite water-based filter cake using hydrochloric acid. Numerous solubility tests were conducted to study the different factors affecting the treatment of hematite such as temperature and particle size. Based on these results, the treatment duration and acid concentration were selected. The high-pressure high-temperature filtration cell was used to build the filter cake and to soak it in the treatment solution at 100°C. Even though the solubility is increasing with acid concentration, however, no significant improvement was noticed above 12.5 vol.% of HCl. The particle size distribution has a considerable effect on the treatment, and the solubility was found to be 86 wt.% for particles finer than 25 microns and 47 wt.% for particle sizes above 75 microns, all in 10 vol.% HCl. The temperature has a significant influence as the solubility doubled when the temperature increased from 75°C to 100°C. The solubility rate decreased with time and reached the maximum in 16 hours which has been taken as treatment duration. Using 12.5 vol.%, 91 wt.% of the filter cake was successfully removed. In the literature comprehensive study on the cleanup of hematite-based filter cakes is lacking. This research provides new insights into hematite removal and address the different factors that impact the treatment efficiency.

Minimizing the Barite Scale in Carbonate Formations during the Filter Cake Removal Process.

The barite scale is one of the most common scales in the oil and gas industry. It can form in the reservoir or precipitate in different production equipment. The formation of such a scale will significantly minimize the capillary diameter of the flow channels and consequently shrink the well productivity. On the other hand, the production of movable barite particles causes severe erosion for the installed equipment. There are several sources of the barite scale such as mixing of incompatible brines and solid invasion of the barite weighted during drilling. In addition, the barite scale could be produced during the interaction of the chelating agent solutions with the reservoir formation during the filter cake removal process (secondary damage). The main focus of this study is to prevent the barite scale inside the carbonate formations during filter cake removal. The capability of a solution consisting of both diethylenetriamine pentaacetic acid (DTPA) and ethylenediamine tetraacetic acid (EDTA) as a novel solution to prevent barite scale formation in carbonate formations after the removal of the barite filter cake was evaluated. A series of laboratory experiments were accomplished to characterize the barite scale and evaluate the performance of the proposed solution. In particular, particle size distribution, scanning electron microscopy, X-ray diffraction, core flooding, NMR spectroscopy, solubility test, and inductively coupled plasma (ICP) spectroscopy tests were conducted for this aim. The experiments were performed using carbonate core samples. The results showed that the proposed solution was able to load 35 000 ppm barium in the presence of calcite ions. The addition of EDTA tended to inhibit the barite deposition and improve the rate of the calcite reaction. NMR results showed that a mixture of DTPA and EDTA (20%) can stimulate the macropores, resulting in an increase in the return permeability by 1.4–1.8 times of the initial value, while the precipitation that occurred in the micropores could be ignored with respect to the overall porosity improvements.

Filter Cake Removal during the Cementing and Completion Stages in CO2 Storage Wells: Current Developments, Challenges, and Prospects

Carbon capture and storage (CCS) technology has become one of the most cost‐effective and promising ways to achieve global climate change mitigation goals. The CO2 storage capacity in depleted oil and gas reservoirs is currently the safest and most economical option. The long‐term sealing of the cement–formation interface in CO2 storage wells (CSW) is essential to avoid CO2 leakage. The filter cake easily affects the interfacial sealing ability, which is a thin impermeable layer formed by drilling fluid residue or solid particles remaining on the borehole wall due to permeable formation. Filter cake removal is essential for favorable cementation and production efficiency. This study highlights the current developments and the main challenges for oil‐ and water‐based mud filter cake removal during the cementing and completion process. Moreover, research ideas and recommendations for various types of filter cake removal are proposed to provide a reference for future work. This information helps deepen understanding with respect to the different filter cake removal options available in the CCS industry and provides a knowledge base that can facilitate the improvement of the cementing quality and production efficiency of existing systems to combat battle CSW safety and production efficiency problems.

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

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

Developing novel bio-nano catalyst well clean up fluid to remove formation damage induced by polymeric water-based drilling fluids

Drilling and completion fluids may cause significant formation damage in oil and gas reservoirs, directly affecting productivity. For many years, operators have applied different stimulation practices such as acidizing, oxidizers, chelating agents, and enzyme treatment to remove formation damage associated with drilling fluids filter cake. An enzyme-based biological treatment was combined with other chemicals or additives as a selective well clean-up practice to improve removing polymer content in the filter cake. However, the secondary formation damage such as deep cleaning of the invaded zone and wettability alteration remained the main concern. This paper presents the development of an innovative clean-up fluid formulation by immobilizing an enzyme and a selective nanoparticle as Bio-Nano Well Clean-Up Fluid (BNWC) in potassium chloride brine to enhance WBM filter cake removal. Several bulk experiments, including; precipitation, iodine test, and viscosity measurement, demonstrate the enzyme's optimization, the nanoparticle concentration, and base fluid brine. BNWC in potassium chloride brine showed the highest HPHT filtration rate at 200 °F and differential pressure of 100 psi and increased the filtration rate by more than 90 percent compared to the conventional enzyme in the same brine. Contact angle measurements confirmed wettability alteration of the carbonate rock to water-wet, and IFT measurements showed higher oil mobility potential. Finally, core flooding tests at reservoir conditions showed a 300 percent enhancement in injection rate and a 50% improvement in core permeability after damage. The immobilization of the enzyme with the nanoparticle has been developed successfully for other applications in bioremediation, farming, and other industries, but the novelty of this research demonstrates the application of nanobiocatalysts in drilling fluids for the first time. This innovative clean-up fluid enhances the enzymatic activity and removes primary and secondary formation damage associated with drilling fluid filter cake.

Ethoxylated Lauryl Alcohol Mixture Applied as Drilling Fluid for Mud Cake Removal: Experimental Design and Formulation Optimization

Ethoxylated Lauryl Alcohol Mixture Applied as Drilling Fluid for Mud Cake Removal: Experimental Design and Formulation Optimization