Permeability Damage Research Articles

Micromechanism and mathematical model of stress sensitivity in tight reservoirs of binary granular medium

Research on reservoir rock stress sensitivity has traditionally focused on unary granular structures, neglecting the binary nature of real reservoirs, especially tight reservoirs. Understanding the stress-sensitive behavior and mathematical characterization of binary granular media remains a challenging task. In this study, we conducted online-NMR experiments to investigate the permeability and porosity evolution as well as stress-sensitive control mechanisms in tight sandy conglomerate samples. The results revealed stress sensitivity coefficients between 0.042 and 0.098 and permeability damage rates ranging from 65.6% to 90.9%, with an average pore compression coefficient of 0.0168–0.0208 MPa−1. Pore-scale compression occurred in three stages: filling, compression, and compaction, with matrix pores playing a dominant role in pore compression. The stress sensitivity of binary granular media was found to be influenced by the support structure and particle properties. High stress sensitivity was associated with small fine particle size, high fines content, high uniformity coefficient of particle size, high plastic deformation, and low Young's modulus. Matrix-supported samples exhibited a high irreversible permeability damage rate (average = 74.2%) and stress sensitivity coefficients (average = 0.089), with pore spaces more slit-like. In contrast, grain-supported samples showed low stress sensitivity coefficients (average = 0.021) at high stress stages. Based on the experiments, we developed a mathematical model for stress sensitivity in binary granular media, considering binary granular properties and nested interactions using Hertz contact deformation and Poiseuille theory. By describing the change in activity content of fines under stress, we characterized the non-stationary state of compressive deformation in the binary granular structure and classified the reservoir into three categories. The model was applied for production prediction using actual data from the Mahu reservoir in China, showing that the energy retention rates of support-dominated, fill-dominated, and matrix-controlled reservoirs should be higher than 70.1%, 88%, and 90.2%, respectively.

The characteristics and effects of Huff-n-Puff in shale with brine, aqueous surfactant solutions and CO2

In this study, we evaluated the permeability damage and throughput potential of shale cores, focusing particularly on the damage water inflicts on shale permeability and the potential for hydrocarbon extraction using various injection media. Nuclear magnetic resonance (NMR) was utilized to analyze the distribution of crude oil across different pore sizes and to determine the limits of their utilization under varied media injection cycles. The results indicate that the Shengli Oilfield FY shale possesses abundant inorganic pores, primarily composed of intergranular and intragranular pores. Organic matter is dispersed and contains numerous micro-fractures. While formation water has only a minor impact on the permeability of fractured cores, it significantly impairs matrix permeability. Moreover, when the formation water content exceeds 10%, the degree of damage will decrease. In contrast to formation water, distilled water causes serious damage to both matrix and fractured cores. Therefore, anti-swelling measures are essential to ensure effective development in subsequent stages. After five injection cycles, the final recovery rates for brine, surfactant, and CO2 injection are 11.5%, 29.3%, and 45.9%, respectively. CO2 injection demonstrates the best production enhancement, followed by surfactant injection. CO2 is particularly effective in each cycle, primarily due to its expansion and extraction mechanism. Surfactants enhance production mainly by reducing interfacial tension and altering wettability, resulting in significant improvement in the first cycle. Meanwhile, brine injection primarily augments production through improved wettability and capillary pressure, resulting in a moderate production improvement. Based on NMR experiments, the minimum pore size for CO2 injection is estimated to be around 10–15 nm, Surfactant injection necessitates pore sizes with a minimum of 30–40 nm and brine injection requires pore sizes of approximately 60–70 nm. This research provides valuable experimental data for on-site shale oil development and deepens our understanding of the mechanisms involved in hydrocarbon recovery from shale using different injection media.

Effect of Combined Chitosan and Hyperbranched Poly-L-Lysine Based Coating on Prolonging the Shelf Life of Oyster Mushroom (Pleurotus ostreatus).

To extend the shelf life of oyster mushroom (Pleurotus ostreatus), the effects of chitosan (CS) and hyperbranched poly-L-lysine (HBPL) combined treatment on quality characteristics, nutritional quality, storage characteristics, and enzyme activity of oyster mushroom during postharvest storage at 4 °C were investigated. The results showed that CS-HBPL combined treatment could significantly reduce rot degree and weight loss and significantly inhibit the browning of oyster mushroom. At the same time, the loss of reducing sugar, vitamin C, soluble protein, and total phenolic was significantly reduced. Compared with the control, CS-HBPL combined treatment could also significantly inhibit an increase in malondialdehyde (MDA) and significantly decrease the relative electrolyte leakage of oyster mushroom. In addition, the activities of catalase (CAT), superoxide dismutase (SOD), phenylalnine ammonialyase (PAL), and peroxidase (POD) were significantly improved, and the activity of polyphenol oxidase (PPO) was significantly inhibited in oyster mushroom. In conclusion, CS-HBPL combined treatment had a good protective effect on the membrane permeability damage of oyster mushroom and could effectively delay the oxidation of phenolic substances and browning of oyster mushroom. Therefore, CS-HBPL combined treatment can be used as a potential strategy to extend the storage time of oyster mushroom.

A Supramolecular Reinforced Gel Fracturing Fluid with Low Permeability Damage Applied in Deep Reservoir Hydraulic Fracturing.

Gel fracturing fluid is the optimum fracturing fluid for proppant suspension, which is commonly applied in deep reservoir hydraulic fracturing. The content of polymers and crosslinkers in gel fracturing fluid is usually high to meet the needs of high-temperature resistance, leading to high costs and reservoir permeability damage caused by incomplete gel-breaking. In this paper, a supramolecular reinforced gel (SRG) fracturing fluid was constructed by strengthening the supramolecular force between polymers. Compared with single network gel (SNG) fracturing fluid, SRG fracturing fluid could possess high elasticity modulus (G' = 12.20 Pa) at lower polymer (0.4 wt%) and crosslinker (0.1 wt%) concentrations. The final viscosity of SRG fracturing fluid was 72.35 mPa·s, meeting the temperature resistance requirement of gel fracturing fluid at 200 °C. The gel-breaking time could be extended to 90-120 min using an encapsulated gel breaker. Gel particles are formed after the gel fracturing fluid is broken. The median particle size of gel particles in the SRG-breaking solution was 126 nm, which was much smaller than that in the industrial gel (IDG) breaking fluid (587 nm). The damage of the SRG-breaking solution to the core permeability was much less than the IDG-breaking solution. The permeability damage of cores caused by the SRG-breaking solutions was only about half that of IDG-breaking solutions at 1 mD.

The Effect of Slickwater on Shale Properties and Main Influencing Factors in Hydraulic Fracturing

As shale gas reservoirs have low porosity and low permeability, hydraulic fracturing is a necessary means for industrial exploitation of shale gas. In this study, aiming at the problem of reservoir damage in the process of hydraulic fracturing of shale gas reservoir, a physical simulation method of slickwater fracturing fluid flow in shale core has been established. The change laws of physical parameters of the shale were quantified after slickwater fracturing fluid filtrating into it. The main factors affecting physical parameters of shale matrix around fractures were found out in the process of fracturing, shut-in, and flowback of slickwater fracturing fluid. The results show that after treated by slickwater fracturing fluid, the wettability of shale becomes more uniform in distribution (the water contact angles from 43° to 48°). In the fracturing filtration zone, the damage rate of fracturing fluid to shale porosity is 6.4%-42.0%. Low differential pressure flowback can reduce the damage of the shale, and prolonging the time of shut-in has no obvious effect on the damage to porosity. After 0.3 d (imbibition stability time), the damage of fracturing fluid to shale permeability is basically stable (55.9%). Permeability damage is mainly caused by residue of the fracturing fluid in large pores and bound water in small pores. Analysis of weights of all fracturing parameters shows that flowback differential pressure has the largest influence weight on shale porosity (51.4%), and well shut-in time has the largest influence weight on shale permeability (62.7%). Therefore, in the production process, it is suggested to properly reduce the backflow differential pressure and moderately shorten the well shut-in time.

Evaluation the effect of wheat nano-biopolymers on the rheological and filtration properties of the drilling fluid: Towards sustainable drilling process

Drilling fluid plays a crucial role in the drilling operation of the oil and gas wells by serving various functions including controlling formation pressures, preserving borehole stability, and removing drill cuttings. However, the loss of the drilling fluid into formations can lead to the permeability damage, groundwater contamination, and altered formation integrity. In addition, the waste generated from drilling activities poses environmental issues, particularly when drilling fluids containing substances, such as heavy metals are discarded. Water-based drilling fluids (WBDFs) are preferred due to their eco-friendliness and cost-effectiveness. However, they suffer from inadequate rheological and filtration properties, prompting the introduction of additives. This study evaluates the use of wheat grain as nano-biodegradable additives in WBDFs, focusing on different sizes of wheat powder ranging from nano to course particle size. Nano-biopolymers (WNBPs) were prepared from breaking down into the nanosized structure using the ball mailing approach and characterized using XRF, FTIR, TGA, DLS, SEM and TEM. Several drilling fluids including the reference, modified, biodegradable and nano-biodegradable drilling fluids were prepared from API SPEC 13A standard, carboxymethyl starch (CMS), wheat powder (WP) at 75–600 µm and nano-biopolymer (WNBPs), respectively. The formulated drilling fluids were investigated by conducting different measurements, such as pH, rheology, filtration and modeling. The obtained results show that the nano-biodegradable exhibited alkaline pH above 10 that keeps the drillpipe and equipment from the corrosion. The developed WNBPs exhibited a significant role in improving the rheological properties of the reference drilling fluid but not effective as CMS. The maximum gel strength of 957.6 pa was obtained from adding 2 wt% WNBPs and increased 1100 pa when temperature increased to 70 °C. Meanwhile, the same wheat nanoparticles enabled increasing the plastic viscosity from 0.03 to 0.09 pa.s and decreased to 0.07 pa.s under the influence of high temperature. In terms of the thinning behavior, the prepared wheat powders exhibited a significant role in providing the thinning behavior of the developed drilling fluids compared with the reference drilling fluid and CMS-modified drilling fluid. Adding 2 wt% WNBPs to the reference drilling fluid decreased the fluid loss from 19.5 to 14 mL but fine WPs have a stronger effective on the filtration properties and lowered the filtration rate to 11.5 mL.

Gestational Fisetin Exerts Neuroprotection by Regulating Mitochondria-Directed Canonical Wnt Signaling, BBB Integrity, and Apoptosis in Prenatal VPA-Induced Rodent Model of Autism.

Embryonic valproic acid (VPA) has been considered a potential risk factor for autism. Majority of studies indicated that targeting autism-associated alterations in VPA-induced autistic model could be promising in defining and designing therapeutics for autism. Numerous investigations in this field investigated the role of canonical Wnt signaling cascade in regulating the pathophysiology of autism. The impaired blood-brain barrier (BBB) permeability and mitochondrial dysfunction are some key implied features of the autistic brain. So, the current study was conducted to target canonical Wnt signaling pathway with a natural polyphenolic modulator cum antioxidant namely fisetin. A single dose of intraperitoneal VPA sodium salt (400 mg/kg) at gestational day 12.5 induced developmental delays, social behaviour impairments (tube dominance test), and anxiety-like behaviour (sucrose preference test) similar to autism. VPA induced mitochondrial damage and over-activated the canonical Wnt signaling which further increased the blood-brain barrier (BBB) disruption, apoptosis, and neuronal damage. Our findings revealed that oral administration of 10 mg/kg gestational fisetin (GD 13-till parturition) improved social and anxiety-like behaviour by modulating the ROS-regulated mitochondrial-canonical Wnt signaling. Moreover, fisetin controls BBB permeability, apoptosis, and neuronal damage in autism model proving its neuroprotective efficacy. Collectively, our findings revealed that fisetin-evoked modulation of the Wnt signaling cascade successfully relieved the associated symptoms of autism along with developmental delays in the model and indicates its potential as a bioceutical against autism.

Rapid assessment of water phase trapping on gas permeability reduction in typical tight gas reservoirs in China

Water phase trapping (WPT) is one of the primary formation damage issues which can cause a steep drop in tight gas production. This paper presented a rapid assessment of the damage potential of WPT in Daniudi, Nanpu 5th, and Keshen 9th tight gas reservoirs involving shallow to ultra-deep layers in China. Typical core samples of the three tight gas reservoirs were selected to perform water imbibition and drainage experiments to mimic the WPT occurrence. After that, the damage degree to core gas permeability induced by WPT was evaluated. Results showed that, for a 16-h vertical water imbibition experiment, the core samples of Daniudi gas reservoir experienced the fastest water imbibition process while the core samples of Keshen 9th gas reservoir established the highest water saturation. After water removal, the ranges of damage degree to core gas permeability induced by the incremental water saturation were 36.07%–78.13%, 36.06%–56.21%, and 61.00%–76.30% in Daniudi, Nanpu 5th, and Keshen 9th tight gas reservoirs, respectively. It found that with the increasing formation depth, tight gas reservoirs can suffer greater damage from WPT not only because of the decline in rock permeability but also the salting out of high salinity formation water. In general, it holds that strong water capillary imbibition phenomenon, low water removal capacity, and high gas permeability damage degree are found to be the striking features of WPT potential on these typical tight gas reservoirs in China.

Research on stress sensitivity of fracture-hole carbonate reservoirs under drilling fluid immersion

Fracture-hole carbonate reservoirs feature the development of multi-scale fractures and dissolution holes. Invasion of drilling fluid into the reservoir and its prolonged interaction with the rock can readily induce a variety of damages, including stress-sensitive damage, consequently diminishing the productivity of oil and gas wells. Experiments were conducted on both dry/wet fractured rock samples and dry/wet fractured rock samples containing holes to investigate the mechanism of stress sensitivity in fracture-hole rocks subjected to fluid soaking. The results indicate that: (1) During the loading process, the highest damage rate to the permeability of fractured rock samples can reach up to 95%. The stress sensitivity coefficients for fracture-hole rock samples with half-hole depths of 2.5 mm, 5.0 mm, and 7.5 mm are 0.58, 0.41, and 0.25, respectively. The permeability damage rate of fracture-hole rock samples soaked with fluid is approximately 80%. (2) As the depth of the hole increases, the stress sensitivity coefficient decreases. The hole's depth is inversely proportional to the maximum stress, while being directly proportional to the maximum displacement of the rock sample. (3) Upon fluid soaking, pressure dissolution occurs within the fractured rock samples, shrinking the fracture width by 15.71–26.17%. (4) Following a 48-h immersion of the rock samples in an alkali solution, decalcification occurs and the pore structure is compromised, thus amplifying the degree of stress sensitivity.

Phase I/II Study to Evaluate the Safety, Feasibility, and Efficacy of FP-1201 (Intravenous Interferon-Beta-1a) to Prevent Toxicities after CD19-Directed CAR T-Cell Therapy: Trial in Progress

BACKGROUND CD19 chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment of patients with relapsed/refractory B-cell malignancies. Yet it remains limited by potentially life-threatening toxicities such as CRS and ICANS. The risk of CRS and ICANS restricts the use of CD19 CAR T-cell therapy to large academic centers and leads to high healthcare resource utilization. Current toxicity prevention strategies have shown limited efficacy to date (prophylactic steroids with axi-cel: CRS, 80%; ICANS, 60%; Oluwole, BJH, 2021; early intervention with brexu-cel: CRS, 89%; ICANS, 60%; Shah, The Lancet, 2021). Our group has shown that endothelial activation and dysfunction are associated with the development of CRS and ICANS, suggesting a key role of increased vascular permeability and blood-brain barrier damage in their pathogenesis (Hay, Blood, 2017). Type-I interferons (IFN-alpha and beta) are major regulators of CD73 expression by endothelial cells, an enzyme critical to the maintenance of endothelial integrity. CD73 breaks down extracellular pro-inflammatory ATP into anti-inflammatory adenosine. In addition, extracellular ATP has been shown to be a major and early driver of systemic inflammation upstream from IL-6 production (Cauwels, Cell Death Dis, 2014), which is associated with severe CRS and ICANS. Preclinical models have demonstrated that IFN-beta-1a treatment is associated with reduced capillary and blood-brain barrier permeability via upregulation of CD73 expression (Floris, J Neuroimmunol, 2002; Kraus., Ann Neurol, 2004; Niemela, Eur J Immunol, 2008). In humans, two recombinant IFN-beta-1a therapies are FDA-approved for the treatment of multiple sclerosis. IFN-beta-1a given intravenously (IV) maximizes the drug's bioavailability and its protective effects on the endothelium. In a study of patients with ARDS, IV IFN-beta-1a (FP-1201 and FP-1201-lyo) was safe and induced CD73 expression (Bellingan, Lancet Respir Med 2014). Given the known effects of IFN-beta-1a on preserving endothelial function and blood-brain barrier integrity, we hypothesize that IV IFN-beta-1a (FP-1201) may prevent CRS and ICANS following CD19 CAR T-cell therapy ( Figure 1A). Since higher rates of severe CRS and ICANS have been reported after axi-cel and brexu-cel, which contain CD28-costimulatory domains, we will restrict the inclusion criteria to patients treated with these products to analyze a population with a higher unmet need and a more homogeneous risk of CRS/ICANS. STUDY DESIGN AND METHODS Objectives and endpoints: Primary objective: To evaluate the safety and feasibility of FP-1201 in patients undergoing treatment with axi-cel or brexu-cel with two co-primary endpoints: i) to estimate the incidence of dose-limiting toxicity rates within the first 14 days following the last administration of FP-1201; ii) to study the type, frequency, and severity of adverse events according to the NCI CTCAE v5.0 from the first administration of FP-1201 and until day +28 after CAR T-cell infusion Secondary objectives: i) To decrease the incidence and severity of ICANS; ii) to decrease the incidence and severity of CRS; iii) to decrease corticosteroid usage; iv) to evaluate the effect of FP-1201 on anti-tumor efficacy Exploratory objectives: To characterize the in vivo effects of FP-1201 on endothelial function, the systemic cytokine milieu, and CAR T-cell function Key inclusion criteria: Adults ≥18 years of age with Karnofsky performance status ≥60% and B-cell non-Hodgkin lymphoma eligible for treatment with axi-cel or brexu-cel Key exclusion criteria: Known hypersensitivity to IFN-beta or major organ dysfunction FP-1201 administration: The FDA-approved IFN-beta-1a Rebif® will be formulated for IV administration (FP-1201). Participants will receive FP-1201 at one of four dose levels detailed in Figure 1B. Statistical design and sample size: We will use a Bayesian Optimal Interval Design to guide the FP-1201 dose escalation. We will plan to treat up to 24 participants. SUMMARY This is a phase I/II study of IV IFN-beta-1a in preventing CRS and ICANS following axi-cel and brexu-cel. The aim is to demonstrate safety and efficacy and to investigate the biologic mechanisms of IFN-beta-1a in preventing endothelial dysfunction.Additional preclinical and preliminary clinical data will be presented at the meeting. This study is registered on clinicaltrials.gov as NCT05936229.

Banaba Restricts Brain Damage: Neuroprotective Role in Cerebral Ischemiareperfusion Injury

Background:: Glucose regulation and energy homeostasis mitigate energy crises milieu in reperfusion injury. We investigated Banaba for its outcomes on cerebral ischemia reperfusion (IR) injury using artery occlusion in rats. The pleiotropic activity of Banaba on various debilitating mechanisms inducing reperfusion injury was evaluated. Aim:: This study aimedto evaluate the pharmacological activity of Banaba (Lagerstroemia speciosa) extract on reperfusion injury and investigate the effect of Banaba on vascular permeability, oxidative stress and cellular damage in ischemia reperfusion injury in rats. Methods:: Transient ischemia and reperfusion through occlusion of the middle cerebral artery (MCAO) lead to Cerebral IR injury in Wistar rats; it was treated with oral administration of Banaba extract (100mg/kg and 200mg/kg). The injury outcomes were evaluated after 22 hours of reperfusion by determining cellular injury, its impact on musculoskeletal coordination, multiple free radical scavenging measures (SOD, GSH, LPO) and vascular permeability of the blood-brain barrier. Result:: Banaba treatment led to a marked improvement in neurological outcomes by enhanced coordination and reduced cerebral infarct in comparison to vehicle control ischemic group. Free radical scavenging activity (SOD and GSH) was significantly better, and lipid peroxidation was reduced by Banaba treatment; it also reduced the vascular permeability of the blood-brain barrier. We observed that a lower dose of Banaba (100 mg/kg) was more effective than the higher (200 mg/kg) in ischemic rats. The anti-inflammatory and anti-oxidant activity could drive the neuroprotective outcomes of Banaba in cerebral IR injury. The critical factor of the beneficial effect of Banaba in cerebral injury is the optimization of dose in this experimental setup of reperfusion injury using rats. Conclusion:: The recovery of injury could be attributed to Banaba’s multi-factorial effect targeting free radicals, inflammation, and necrosis during ischemiareperfusion injury.

Investigation of Carbonate Matrix Damage and Remediation Methods for Preformed Particle Gel Conformance Control Treatments

Summary Preformed particle gels (PPGs) have been widely applied to control excessive water production in mature oil fields with fractures or fracture-like features, especially in sandstones, but with limited attention to carbonates. However, a vital concern arises regarding the potential damage of PPGs on the adjacent matrix that might promote negative results. This paper comprehensively evaluates PPGs’ potential damage to the carbonate matrix and seeks design optimization solutions. Filtration tests were applied to compare PPGs’ penetration into the matrix under different sets of conditions. The filtration regimes were defined by filtration curves, and the gel damage on the matrix was determined by permeability measurement results. Experiments were conducted to investigate the efficiency of an oxidizer as a remediation method to remove the damage. The qualitative description of gel particles’ invasion and plugging behavior in the carbonate matrix was presented based on the analysis of filtration test results and permeability measurements. The results show that the swollen gel filtration curves can be divided into three regions: prior-filter-cake, filter-cake-building, and stable stages according to the gel particles’ response to the injection pressure and effluent flow rates. PPGs can form cakes on the rock surface to prevent particles’ further penetration into the carbonate matrix, and the penetration was only limited to less than a few millimeters. The smallest gel particles (50–70 US mesh size) were more likely to form external and internal filter cakes at higher pressure values (700 psi) and result in more damage to the matrix. To restore the matrix permeability after filtration tests, oxidizer soaking proved to be a reliable solution. In all, the results indicated that unintentional matrix permeability damage induced by gel injection is generally unavoidable but conditionally treatable.

Pore-Scale Analysis of the Permeability Damage and Recovery during Cyclic Freshwater and Brine Injection in Porous Media Containing Non-Swelling Clays

Permeability damage in subsurface porous media caused by clay mobilization is encountered in many engineering applications, such as geothermal energy, water disposal, oil recovery, and underground CO2 storage. During the freshwater injection into rocks containing brine, the sudden decrease in salinity causes native clay fines to detach and clog pore throats, leading to a significant decline in permeability. The clay fines detach due to weakened net-attractive forces binding them to each other and the grain. Past experiments link this permeability damage on the immediate history of the salinity and the direction of flow. To better understand this phenomenon, we conducted pore-scale simulations of cyclic injection of freshwater and brine into sandstone containing Kaolinite clay. Our simulations establish a link between the clay-fine trajectory and the permeability trend observed by Khilar and Fogler (1983). For a uniform clay size of 3 microns, we observe a permeability decline by two orders of magnitude during freshwater injection with respect to brine injection. Increasing salinity and simultaneously reversing flow direction restores the permeability. The permeability restoration upon reversing the brine flow direction is attributed to the unblocking of pore throats in the reverse direction by the movement of the clay particles along the grain surfaces by the hydrodynamic force and the strong net-attractive force under high salinity.

Study on permeability evolution and damage mechanism along the EGS fracture in heat mining stage under thermal stress/cracking

As main heat exchange channel in enhanced geothermal system, the evolution of hydraulic conductivity in fracture is significance for efficient heat mining. For the thermal stress or thermal cracking spontaneously induced by the temperature difference between low-temperature fluid and hot rock in heat mining stage, it is necessary to explore the damage mechanism along EGS fracture and the corresponding permeability evolution. Firstly, the long-term permeability tests under high temperature (50–200 ℃) were conducted by the self-developed high temperature seepage experimental device. Then, a coupled THM-D model was constructed to describe the damage distribution along fracture. Combined with experimental and simulation results, relationship between the thermal stress/cracking and the evolution of fracture permeability is revealed. The results indicate that during high-temperature (200 ℃) experiments, the fracture permeability first increases rapidly under the low-temperature induced thermal stress/cracking, then decreases due to the blockage effect induced by the debris particles generated in thermal cracking along fracture. The enhancement of injection velocity and heterogeneity are all conducive to the emergence of thermal cracking in matrix along fracture. Simultaneously, high confining pressure has a negative effect on the migration of debris particles of thermal cracking, which contribute to prevent the blockage of debris particles.

The Reservoir Sensitivity of Triassic Baikouquan Formation in Mahu Depression

The Triassic Baikouquan Formation in the slope area of the Mahu Depression is the largest glutenite reservoir in the Junggar Basin, with low porosity and permeability; however, its physical properties are poor, the distribution of oil and gas is quite different, and the output fluctuates greatly. It is of great guiding significance to study the sensitivity characteristics of the reservoir for oil and gas development and productivity design. In this paper, the reservoir of the Triassic Baikouquan Formation in the Mahu Depression of Junggar Basin is taken as the research object, and the geological characteristics, pore structure characteristics and clay mineral characteristics of the reservoir are investigated through the use of X-ray diffraction and scanning electron microscope; moreover, the sensitivity of velocity, water, salt and stress of the reservoir are studied through the use of a sensitive flow test. The research results show that the lithology of the reservoir is mainly glutenite, composed of tuff and metamorphic mudstone, and the minerals are mainly Yimeng mixed-layer clay minerals, with fine particle size, average porosity of 10.5% and an average permeability of 9 × 10−4 μ m2, forming pore structures such as dissolved pores, cemented pores and intergranular gaps, which belong to the poor pore structure reservoir with low porosity and low permeability. The velocity-sensitive damage rate of reservoirs in the study area is between 4 and 46, and the reservoirs are moderately weak and poor in velocity sensitivity. The damage rate of the reservoirs’ water sensitivity in the study area is between 36 and 58, which can be defined as medium–weak and medium–strong water sensitivity. The reservoir in the study area contains clay minerals in a Yimeng mixed layer, which easily hydrate and swell, and the clay minerals in different parts of the Yimeng mixed layer are different, resulting in great differences in salt sensitivity at different depths. The maximum permeability damage rate of the reservoir is 80%, the irreversible permeability damage rate is 20%, and the stress sensitivity is weak. The research results provide theoretical data support for adopting targeted reservoir protection measures in the process of oil and gas exploration, development and construction.

Investigation of the Effect of Fracturing Fluids on Shale Pore Structure by Nuclear Magnetic Resonance

Hydraulic fracturing technology significantly enhances the productivity of shale oil and gas reservoirs. Nonetheless, the infiltration of fracturing fluid into shale formations can detrimentally affect the microscopic pore structure, thereby impairing the efficacy of hydraulic stimulation. In this study, nuclear magnetic resonance (NMR) technology was utilized to conduct high-pressure soaking tests on shale specimens treated with EM30+ + guar gum mixed water and CNI nano variable-viscosity slickwater, where various concentrations of a drag reducer were utilized. Additionally, the differences in porosity, permeability, mineral composition, and iron ion concentration before and after the measurements were compared, which were used to analyze the influence on the shale’s microscopic pore structure. It features a reduction in the total pore volume after the interaction with the fracturing fluid, with the pore-throat damage degree, porosity damage degree, and permeability damage degree ranging from 0.63% to 5.62%, 1.51% to 6.84%, and 4.17% to 19.61%, respectively. Notably, EM30+ + guar gum mixed water exhibits heightened adsorption retention, alkaline dissolution, and precipitation compared to CNI nano variable-viscosity slickwater, rendering it more deleterious to shale. Moreover, higher concentrations of drag reducers, such as EM30+ or CNI-B, predominantly result in damage to the shale’s micropores. Shale compositions characterized by lower content of quartz and elevated proportions of clay minerals and iron-bearing minerals showcase augmented mineral dissolution and precipitation, consequently intensifying the shale damage. The hydration expansion of mixed-layer illite/smectite profoundly diminishes the core permeability. Consequently, the mechanisms underpinning the damage inflicted on shale’s microscopic pore structure primarily involve fracturing fluid adsorption and retention, mineral dissolution, and precipitation, such as clay minerals and iron-containing minerals.

Small extracellular vesicles derived from umbilical cord mesenchymal stem cells repair blood-spinal cord barrier disruption after spinal cord injury through down-regulation of Endothelin-1 in rats

Spinal cord injury could cause irreversible neurological dysfunction by destroying the blood-spinal cord barrier (BSCB) and allowing blood cells like neutrophils and macrophages to infiltrate the spinal cord. Small extracellular vesicles (sEVs) derived from mesenchymal stem cells (MSCs) found in the human umbilical cord have emerged as a potential therapeutic alternative to cell-based treatments. This study aimed to investigate the mechanism underlying the alterations in the BSCB permeability by human umbilical cord MSC-derived sEVs (hUC-MSCs-sEVs) after SCI. First, we used hUC-MSCs-sEVs to treat SCI rat models, demonstrating their ability to inhibit BSCB permeability damage, improve neurological repair, and reduce SCI-induced upregulation of prepro-endothelin-1 (prepro-ET-1) mRNA and endothelin-1 (ET-1) peptide expression. Subsequently, we confirmed that hUC-MSCs-sEVs could alleviate cell junction destruction and downregulate MMP-2 and MMP-9 expression after SCI, contributing to BSCB repair through ET-1 inhibition. Finally, we established an in vitro model of BSCB using human brain microvascular endothelial cells and verified that hUC-MSCs-sEVs could increase the expression of junction proteins in endothelial cells after oxygen-glucose deprivation by ET-1 downregulation. This study indicates that hUC-MSCs-sEVs could help maintain BSCB’s structural integrity and promote functional recovery by suppressing ET-1 expression.

Modeling of formation damage during smart water flooding in sandstone reservoirs

Impairment of permeability has been observed as an effective factor in production decline during secondary and tertiary recovery processes such as water flooding. Among different permeability damage mechanisms, fines migration and deposition is known as the main mechanism which occurs due to pore throat clogging and blocking. Because injected water and formation water are usually incompatible, permeability damage evaluation and scale formation prediction must be done before the water flooding process in the oil field is implemented. For this purpose, compatibility tests and core flood experiments are common, but experimental approaches with time and facility limitations are expensive. Thus, by decreasing the time required for conducting experiments, modeling approaches can replace the routine laboratory experiments. Based on thermodynamic balance and the solubility of ions in water, scale development due to seawater injection in an Iranian oil field was predicted in this work using the OLI ScaleChem software. After that, it was suggested that special water be introduced to help reduce the amount of scales that had accumulated in the rock pore space. The extent of permeability damage in various seawater injection scenarios was then assessed via dynamic core flood experiments. Finally, scales-seawater injection into the core was simulated using digital core analysis (DCA) results and the pore scale modeling approach. The core flood experiment data are consistent with the scale formation prediction made by the OLI ScaleChem software, which indicates that smart water can be determined by optimizing the salinity and ion content of injected water. Also, results of permeability damage prediction by our modeling approach have good agreement with the core flood experiment data. Therefore, our modeling approach can replace the conventional core flood experiments as a low-cost method with high computational efficiency and high enough accuracy to evaluate formation damage in the water flooding process.

Fine particle liberation in saturated porous media under non-isothermalfluid flow

Decline in well productivity is a widely reported phenomenon and a critical challenge negatively impacting energy and water operations in deep geological reservoirs [1, 2]. A key contributor to this problem is the detachment of in-situ fine particles present in the porous matrix, which will then migrate and travel through the porous formation until getting strained within thin pore throats resulting in pore clogging and therefore permeability damage [3]. The detachment of in-situ fine particle occurs when the mechanical equilibrium of the attaching (i.e., electrostatic and gravity forces) and the detaching forces (i.e., drag and lifting forces) exerted on the particle is disturbed. In geological reservoirs, the equilibrium of in-situ fines can be disturbed as a result of fluid flow velocities, temperature alterations in the porous formation, or reduced ionic strength of the in-situ fluids [4]. Fines migration and straining can also alter in-situ stresses through generating pore pressure changes as a result of permeability damage [5].
 Multiple experimental and numerical studies have evaluated the mechanisms involved in detachment, migration, and straining of in-situ fines and the clogging of pore fluid channels [6, 7]. A number of studies have also focused on evaluating temperature-induced particle mobilization [8]. Variations of the electrostatic force with temperature is often explained through the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory [9]. In a saturated porous formation containing in-situ fines, Dielectric permittivity of pore fluid decreases with an increase in temperature, weakening the repulsion between the fine clay particles and the sand surface [10]. As a result, the attaching electrostatic forces are lower under higher temperatures.
 This study focuses on developing a theoretical model to evaluate the impact of the size distribution of in-situ fine particles on non-isothermal fluid flow induced fine mobilization in saturated porous media. Expressions for drag force and electrostatic force are obtained based on the DLVO theory considering coupled effects of fluid velocity, temperature, and ionic strength of in-situ fluids. The main parameters adopted in the proposed model are presented in Table 1. The proposed model predicts the maximum concentration of retained fines considering coupled effects from temperatures and pore pressures. Results are valuable for estimating permeability damage and well productivity during enhanced geothermal operations.

Study on Matrix Damage and Control Methods of Fracturing Fluid on Tight Sandstone Gas Reservoirs.

Hydraulic fracturing is a highly effective method for stimulating the development of gas reservoirs. However, the process of pumping fracturing fluid (FF) into the reservoir unavoidably causes damage to the surrounding matrix, leading to a decrease in the overall stimulation effect. To assess the extent of matrix permeability damage caused by the intrusion of FF, as well as its impact on the pore throat structure, and to propose appropriate measures to control this damage, we conducted a series of experimental studies on tight gas reservoirs. These studies included mercury intrusion, core flow, nitrogen adsorption, linear expansion, and contact angle measurements. The findings revealed that the damage inflicted on matrix permeability by FF was significantly greater than that caused by its gel-breaking counterpart. Surprisingly, the damage rate of the rejecting fluid to the matrix was found to be comparable to that of its gel-breaking counterpart. The fractal dimension (D2) was observed to have a strong correlation with surface area, pore volume, and mean pore size, making it an effective means of characterizing pore structure characteristics. After the rock samples were displaced by the formation water, the D2 value decreased, leading to a decrease in the complexity of the pore throat structure and an increase in matrix permeability. Conversely, the displacement of the FF increased the D2 value, indicating a gradual complication of the pore throat structure and a more uneven distribution of pore sizes. The inclusion of polyamide in antiexpansion FF, as well as its gel-breaking counterpart, proved to be effective in inhibiting the hydration and expansion of clay minerals, thereby reducing water-sensitive damage. Additionally, the use of surfactants with low surface tension enhanced the flowback rate of FF by increasing the contact angle and reducing the work of adhesion. This, in turn, helped to decrease the apparent water film thickness and expand gas flow channels, ultimately improving gas permeability.