SPE JournalPub Date : 2024-02-01DOI: 10.2118/218422-pa
Dmitry Chuprakov, A. Peshcherenko, Mikhail Anisimov
{"title":"Coupled Geomechanics and Chemistry Model for Acid Stimulation of Naturally Fractured Carbonate Reservoirs","authors":"Dmitry Chuprakov, A. Peshcherenko, Mikhail Anisimov","doi":"10.2118/218422-pa","DOIUrl":"https://doi.org/10.2118/218422-pa","url":null,"abstract":"\u0000 Treatments of naturally fractured carbonate formations typically involve acid injection when damage of natural fractures (NFs) occurs mechanically and chemically. Coupled modeling of both mechanisms is often neglected. We build a quantitative model of damageable reservoir, where the permeability depends on the shear and tensile activation of NFs, as well as acid transport and reaction. Simulations demonstrate model applicability to NF acidizing and acid fracturing. Particularly, we show that strong pressure drawdowns in tight carbonates result in steep production declines because of NF pinching.","PeriodicalId":22252,"journal":{"name":"SPE Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140470306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SPE JournalPub Date : 2024-02-01DOI: 10.2118/211451-pa
J. Leon, S. K. Masalmeh, A. M. AlSumaiti, M. Baslaib
{"title":"Assessment of World’s First Two Polymer Injectivity Tests Performed in Two Giant High-Temperature/High-Salinity Carbonate Reservoirs Using Single-Well Simulation Models and Pressure Falloff Tests Analysis","authors":"J. Leon, S. K. Masalmeh, A. M. AlSumaiti, M. Baslaib","doi":"10.2118/211451-pa","DOIUrl":"https://doi.org/10.2118/211451-pa","url":null,"abstract":"\u0000 Polymer flooding is a mature enhanced oil recovery (EOR) technology that has been widely implemented around the world for more than 60 years. Polymer flooding mostly targets medium- to high-permeability sandstone reservoirs with moderate salinity, hardness, and temperatures. However, in the last few years, the envelope of polymer flooding has been expanded to harsher reservoir conditions of high-temperature and high-salinity mixed-wet to oil-wet heterogeneous carbonate reservoirs. Development of novel polymers and innovative field application concepts has allowed for the reconsideration of polymer-based EOR as a promising technology to improve sweep efficiency for these challenging reservoirs. Polymer injectivity is one of the key challenges for polymer flooding projects and requires a rigorous derisking program that includes laboratory and field testing. A comprehensive laboratory program was designed to assess and investigate polymer thermal stability, polymer rheology in porous media, adsorption, and injectivity using reservoir core samples. In addition, two polymer injectivity tests (PITs) were performed in two giant light oil (0.3 cp) carbonate reservoirs in onshore Abu Dhabi under harsh conditions of high salinity (>200 g/L), high divalent ions (>20 g/L), high temperature (>250°F), and H2S concentration of up to 40 ppm. The polymer used during the two PITs (PIT 1 2019 and PIT 2 2021) is a new generation of EOR polymer (SAV 10) with high 2-acrylamido-tertiary-butyl sulfonic acid content that was specifically developed to tolerate such harsh conditions. This paper is focused on the interpretation of the PITs and lessons learned for future polymer-based EOR projects. The detailed data acquired in both tests were used to evaluate the polymer injectivity at representative field conditions and in-depth mobility reduction. The PITs together with the extensive laboratory studies are part of a thorough derisking program for the upcoming world’s first innovative hybrid EOR multiwell pilots—simultaneous injection of miscible gas and polymer (SIMGAP) and simultaneous injection of water and polymer (SIWAP).\u0000 Both PITs are composed of three stages that include a multirate waterflood baseline, polymer injection using different rates, and polymer concentrations followed by extended chase waterflooding. In addition, a sequence of multiple pressure falloff (PFO) tests was acquired during the PIT executions and analyzed to obtain the required uncertainty parameters for the history-matching exercise. Polymer preshearing was considered as part of both PIT programs with the aim to homogenize the polymer molecular weight distribution and reduce possible shear-thickening effects near the wellbore as per laboratory measurements. Two single-well 3D simulation models were built to incorporate the information from polymer laboratory studies and to interpret the large field data sets acquired during the PITs. Lessons learned from PIT 1 allowed us to optimize the PIT ","PeriodicalId":22252,"journal":{"name":"SPE Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139966628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SPE JournalPub Date : 2024-02-01DOI: 10.2118/219478-pa
Han Wang, Jinsong Huang, Shiyuan Zhan, Mingshan Zhang, Jianchao Cai
{"title":"Study on CO2 and CH4 Competitive Adsorption in Shale Organic and Clay Porous Media from Molecular- to Pore-Scale Simulation","authors":"Han Wang, Jinsong Huang, Shiyuan Zhan, Mingshan Zhang, Jianchao Cai","doi":"10.2118/219478-pa","DOIUrl":"https://doi.org/10.2118/219478-pa","url":null,"abstract":"\u0000 The elucidation of the competitive adsorption behaviors between CO2 and CH4 holds great importance in the context of improving natural gas recovery in shale reservoirs. Shale rock, as a complex porous medium, exhibits a highly interconnected multiscale pore network with pore size spanning from several to tens of nanometers. Nevertheless, accurately capturing the adsorption effects and studying the CO2/CH4 competitive adsorption within a large-scale, realistic, 3D nanoporous matrix remains a significant challenge. In this paper, we proposed a novel lattice Boltzmann method (LBM) coupled molecular simulation to investigate CO2/CH4 competitive adsorption in 3D shale nanoporous media. The initial step involves conducting Grand Canonical Monte Carlo (GCMC) simulations to simulate the competitive adsorption behaviors of CO2 and CH4 in kerogen and illite slit pores, with the aim of obtaining the atomic density distribution. Subsequently, a Shan-Chen-based lattice Boltzmann (LB) simulation is used under identical conditions. By coupling the molecular simulation results, the fluid-solid interaction parameters are determined. Finally, LB simulations are performed in designed 3D porous media, utilizing the fluid-solid interaction parameters. The effects of mineral type, CO2 concentration, and pore structure on competitive adsorption behaviors are discussed carefully. Our research offers significant contributions to the improvement of gas recovery and carbon geological sequestration through the examination of CO2/CH4 competitive adsorption in nanoporous media. Additionally, it serves as a link between molecular and pore-scale phenomena by leveraging the benefits of both molecular simulations and pore-scale simulations.","PeriodicalId":22252,"journal":{"name":"SPE Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140463574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SPE JournalPub Date : 2024-02-01DOI: 10.2118/219476-pa
M. Desouky, Y. Samarkin, M. Aljawad, A. Amao, M. AlTammar, K. Alruwaili
{"title":"Diammonium Phosphate Treatment for Sustained Hydraulic/Acid Fracture Conductivity in Chalk and Limestone Formations","authors":"M. Desouky, Y. Samarkin, M. Aljawad, A. Amao, M. AlTammar, K. Alruwaili","doi":"10.2118/219476-pa","DOIUrl":"https://doi.org/10.2118/219476-pa","url":null,"abstract":"\u0000 The sustained conductivity of hydraulic/acid fractures is crucial for the continuous and effective production of hydrocarbons. However, hydraulic fractures in soft carbonate formations often experience a reduction in conductivity due to rock deformation and creeping under in-situ stresses. One approach to resolve this issue is to stiffen the fracture surfaces using a consolidating agent. This study examines the application of diammonium hydrogen phosphate (DAP) as an additive to improve the hydraulic/acid fracture conductivity in Indiana limestone and Austin chalk slabs. Initially, flat slabs of Indiana limestone and Austin chalk were subjected to acidization using 15% and 10% hydrochloric acid (HCl) for 10 minutes and 5 minutes, respectively. The resulting surface texture changes were measured using a profilometer. Subsequently, half of the samples underwent treatment in 1 M DAP under 1,000 psi and 75°C for 72 hours. The surface stiffness of the samples was evaluated using nondestructive impulse hammering before and after acid injection and DAP treatment, while hydraulic/acid fracture conductivity was determined using an API conductivity setup. Following acid injection, the experimental results demonstrate that the stiffness of all the samples was diminished to different degrees. However, intact Indiana limestone samples exhibited increased stiffness after treatment with DAP. Acidized Indiana limestone samples showed partial restoration of their original stiffness with DAP treatment. In contrast, DAP treatment fully restored the stiffness of Austin chalk samples and further enhanced it, resulting in a twofold to fivefold increase. The increased stiffness observed in the treated samples had a direct impact on short- and long-term conductivity. Treated Indiana limestone fractures exhibited double the conductivity of untreated fractures. The improvement in Austin chalk conductivity was even more significant after DAP treatment, resulting in seven to eight times higher conductivity in the treated hydraulic/acid fractures. It is worth noting that there was little to no correlation between surface roughness and conductivity, highlighting the significant influence of fracture stiffness on conductivity.","PeriodicalId":22252,"journal":{"name":"SPE Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140469411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SPE JournalPub Date : 2024-02-01DOI: 10.2118/219481-pa
Jinfei Sun, Fujie Yang, Ben Qi, Zaoyuan Li, Jin Li
{"title":"A New Calculation Model for Equivalent Circulating Density Considering Interface Effect between Various Fluids during Cementing Process","authors":"Jinfei Sun, Fujie Yang, Ben Qi, Zaoyuan Li, Jin Li","doi":"10.2118/219481-pa","DOIUrl":"https://doi.org/10.2118/219481-pa","url":null,"abstract":"\u0000 Equivalent circulating density (ECD) is an essential parameter in the construction of oil and gas wells, which can be used to control the downhole pressure and prevent serious incidents such as well leakage or blowouts. Different engineering tasks will lead to changes in the ECD calculation model; the classical pipe flow theory can be used to calculate the ECD of circulating drilling fluid, but it is not suitable for the cementing displacement because it does not consider the interface effect between various fluids. In this paper, a new ECD calculation model has been developed that accounts for the changes in fluid interface morphology between displacing fluid and displaced fluid during the cementing process. Moreover, a simulation of the effects of borehole radius, casing eccentricity, displaced fluid density, and flow rate on the ECD were analyzed and quantified by a numerical approach to solve the fluid dynamics equilibrium equations that describe the flow in the eccentric annuli based on the semi-implicit method for pressure-linked equations (SIMPLE) algorithm. The results show that the calculated ECD predicted by the proposed model is larger than the traditional model with the reduction in the borehole radius, and the maximum deviation at the inlet position can reach 0.03 g·cm−3. Variation in the length of the interface transition zone is the main reason for the deviation in ECD prediction accuracy. In the case of constant casing outer diameter, fluid rheology, and displaced fluid density, the ECD decreases with increasing borehole radius. Meanwhile, it increases with higher displaced fluid density, eccentricity, and annular velocity. It is also shown that the length of the mixing zone can reach up to 40% of the pipe length under the conditions of eccentricity and displacement described in the paper. The proposed model predicts the ECD in the annulus by considering the influence of different engineering parameters on the movement of displacement interface, which can effectively ensure the safety of the cementing operation.","PeriodicalId":22252,"journal":{"name":"SPE Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140470356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SPE JournalPub Date : 2024-02-01DOI: 10.2118/219480-pa
Jun Qu, Qilong Xue, Jin Wang, Jinchao Sun, Jintao Lu, Haiping Zhang, Feng Sun, Xinghua Tao
{"title":"From Design to Experimental Validation of the Fully Mechanical Gravity Tool Face Measurement-While-Drilling System","authors":"Jun Qu, Qilong Xue, Jin Wang, Jinchao Sun, Jintao Lu, Haiping Zhang, Feng Sun, Xinghua Tao","doi":"10.2118/219480-pa","DOIUrl":"https://doi.org/10.2118/219480-pa","url":null,"abstract":"\u0000 Exploiting geothermal resources such as hot dry rocks (HDRs) requires directional drilling technology. Measurement-while-drilling (MWD) technology plays a crucial role in directional measurement. However, its high temperature and environment limit downhole measurement instruments in application. For this research, we designed an MWD system with a mechanical gravity tool face, and the fully mechanical structure was used to overcome the high-temperature constraints. The bias stabilization platform, gravity tool face coding method, and mud pulse generation structure were designed. The eccentric stable model and pulse generation structure model were established through numerical analysis, and a gravity tool face angle coding and identification method was also established. The experimental prototype testing system was built on theoretical analysis and hydrodynamics. The feasibility of the tool functions and the recognition algorithm were verified experimentally, with a maximum measurement error of 6° and an average measurement error of 2.6°. The average measurement error of the system in the well test is 6°, which verifies the reliability of the system.","PeriodicalId":22252,"journal":{"name":"SPE Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140465487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SPE JournalPub Date : 2024-02-01DOI: 10.2118/219464-pa
Fangxuan Chen, Shihao Wang, H. Nasrabadi
{"title":"Molecular Insights of Excessive Water Cut during Cyclic Gas Injection in Liquid-Rich Shale Reservoirs: Contributions of Hydrocarbon Condensation and Water Trapping","authors":"Fangxuan Chen, Shihao Wang, H. Nasrabadi","doi":"10.2118/219464-pa","DOIUrl":"https://doi.org/10.2118/219464-pa","url":null,"abstract":"\u0000 In a recent pilot test of cyclic gas injection (huff ‘n’ puff) in a Permian shale reservoir, excessive water product was observed, the reason for which remains unclear. In this work, we analyze the mechanisms of gas huff ‘n’ puff processes using molecular dynamics (MD) simulations and explain the reason for the high water-cut phenomenon. We aim to investigate the hydrocarbon-water-rock interactions during the gas injection as well as production within a shale rock in the pore scale. To mimic the heterogeneous pore structure of the shale rock, we have designed a pore system, including a bulk pore, a pore throat, and a dead-end pore. We simulate the distribution of different fluids during the initial equilibrium stage, the primary depletion stage, and the huff ’n’ puff stage. The results show that an excessive amount of water is trapped by the condensation mechanism in the larger pores during the primary depletion stage. The water is then recovered with the injection of working (lean) gases. Moreover, we have analyzed the effect of different injection gases (IGs) and found that carbon dioxide (CO2) yields a higher water cut compared with methane (C1). Moreover, our findings have revealed the trapping mechanisms of hydrocarbon-water mixtures in shale rocks and have highlighted the impacts of pore structures on the recovery of shale reservoirs. As such, we have provided a potential explanation of the observed phenomenon.","PeriodicalId":22252,"journal":{"name":"SPE Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140470459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SPE JournalPub Date : 2024-02-01DOI: 10.2118/219483-pa
Jun Zhao, Wenjun Huang, Deli Gao
{"title":"Interaction between Pipe Rotation and Cuttings Transport in Extended-Reach Drilling: Mechanism, Model, and Applications","authors":"Jun Zhao, Wenjun Huang, Deli Gao","doi":"10.2118/219483-pa","DOIUrl":"https://doi.org/10.2118/219483-pa","url":null,"abstract":"\u0000 High drag and torque on drillstring and difficulty in hole cleaning are two major challenges in extended-reach drilling, and these two challenges are usually coupled with each other. However, previous studies considered the drillstring mechanics and hole cleaning as two relatively independent issues and studied them separately, which cannot fully reveal the complex mechanisms of pipe sticking and obtain proper drilling parameters to ensure hole cleaning and reduce drag and torque. To solve this problem, in this paper we present the concept of pipe-cuttings interaction and elaborate on the two interaction mechanisms, which are the effect of pipe rotation on cuttings transport and the effect of cuttings distribution on pipe load. Second, we introduce the stirring diffusion factor and pipe-cuttings contact stress to quantify the pipe-cuttings interaction, and we obtain their mathematical expressions through nonlinear regression of numerical simulation results. Third, we establish the mechanical pipe-cuttings interaction model by modifying and combining the tubular mechanical model and the cuttings transport model. Finally, we validate the interaction model and apply it to a case study of extended-reach drilling in the South China Sea. The results show that the interaction model is of high prediction accuracy and is superior to the conventional tubular mechanical and cuttings transport models because the interaction between pipe rotation and cuttings transport is sufficiently considered. The problem of poor hole cleaning for a 12¼-in. section is serious, and pipe sticking occurs frequently for the extended-reach well in the case study because the stationary bed height is more than 10% in actual drilling. It is usually difficult to ensure hole cleaning of a 12¼-in. section by only optimizing a single parameter of rate of penetration (ROP), flow rate, or rotational speed, but optimizing two of the parameters at the same time can achieve better results. Lastly, we establish a recommended chart of drilling parameters, which can aid engineers in making comprehensive recommendations on drilling parameters.","PeriodicalId":22252,"journal":{"name":"SPE Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140465363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SPE JournalPub Date : 2024-02-01DOI: 10.2118/219466-pa
Shuo Yang, Pengcheng Liu, Song Deng, Yanwei Wang
{"title":"Oil Detachment Mechanism in Natural Surfactant Flooding from Silica Surface: Molecular Dynamics Simulation","authors":"Shuo Yang, Pengcheng Liu, Song Deng, Yanwei Wang","doi":"10.2118/219466-pa","DOIUrl":"https://doi.org/10.2118/219466-pa","url":null,"abstract":"\u0000 International regulations have compelled Europe and the United States to phase out certain traditional surfactants to mitigate the use of toxic and nonbiodegradable chemicals. Sodium cocoyl propionate (SCA), as a natural surfactant with high performance, has been proved to have the potential to replace traditional surfactants in previous studies. However, its performance has not fully met practical application requirements. Therefore, in this paper, molecular dynamics (MD) simulation was used to study the detachment behavior and mechanism of SCA, lauryl dimethylamine oxide (OA-12), emulsifier OP-10, and SOO (combination of SCA, OA-12, and OP-10) on crude oil (dodecane, C12) at different temperatures (80–120°C) and salinities (20 000–200 000 mg/L). The complex interaction mechanism between surfactant molecules and C12 molecules was revealed by analyzing the simulated snapshot, radial distribution function (RDF), mean square displacement (MSD), and interaction energy. The simulated snapshot captures the conformational evolution of surfactant molecules at different time points, emphasizing the spatiotemporal and spatial changes of their dynamic behavior. A comparison of two desorption modes reveals that dispersive adsorption displacement and concentrated adsorption displacement are two possible desorption mechanisms. RDF analysis shows that the probability of SOO molecules near C12 remains high even at high-salinity and -temperature conditions. MSD analysis showed that the diffusion capacity of SOO was the highest at 100°C, reaching 1.52867×10 –5 cm2/ps. The calculation of interaction energy results reveals that SOO has a strong adsorption capacity for C12, which is mainly due to the effect of van der Waals (vdW) force. This is because the C12 molecules are inert, and their molecular movement is mainly determined by the polar groups of the surfactant. The main contribution of this study is to provide a natural surfactant with superior performance as a viable alternative, offering experimental settings for further improvement in SCA performance. This research provides theoretical guidance for on-site applications of SCA and SOO to enhance oil recovery.","PeriodicalId":22252,"journal":{"name":"SPE Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139965731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SPE JournalPub Date : 2024-02-01DOI: 10.2118/219470-pa
Y. Nie, Bisheng Wu, Guangqing Zhang, Li Zhang, Shiyuan Li, Liu Yang, Zhaoyang Liu
{"title":"Determination of the Thickness and Fracture Toughness of Shale Interfacial Transition Zone Near Various Micromineral Aggregates Using Nano-Scratch Tests","authors":"Y. Nie, Bisheng Wu, Guangqing Zhang, Li Zhang, Shiyuan Li, Liu Yang, Zhaoyang Liu","doi":"10.2118/219470-pa","DOIUrl":"https://doi.org/10.2118/219470-pa","url":null,"abstract":"\u0000 Heterogeneously distributed micromineral aggregates (MMAs) are common in shale reservoirs. The interfaces between these MMAs and the surrounding minerals significantly affect fracture propagation behaviors during shale oil exploitation. In this paper, the concept of interfacial transition zone (ITZ) between the MMAs (e.g., striped barite, pyrite, calcite, apatite blocks, and bedding plane) and the surrounding mineral in shale is introduced. Due to the small thickness of the ITZ, its thickness and mechanical properties are very difficult to determine by traditional standard methods. To address this issue, this paper proposes a method combining nano-scratch tests, scanning electron microscopy (SEM), and quantitative evaluation of minerals by SEM (QEMSCAN) techniques to investigate the thickness and fracture toughness of the ITZ near typical MMAs. The results show that the thickness of the ITZ determined by the transverse force FT and scratch depth (-d2) varies from 3.2 μm to 17.3 μm. In addition, the fracture toughness of both MMAs and ITZs is characterized by high heterogeneity ranging from 0.1 MPa·m0.5 to 2.1 MPa·m0.5. Moreover, a formula evaluating the fracture toughness of the ITZ is proposed taking into account the type and content of minerals in the ITZ. A strong linear relationship is observed between the thickness of the ITZ and the average fracture toughness ratio. In addition, a relationship is established between the fracture toughness of the ITZ and MMAs, and an evaluation equation is derived. This study is helpful for understanding the characteristics (i.e., mainly thickness and fracture toughness) of the ITZ within shales.","PeriodicalId":22252,"journal":{"name":"SPE Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140465128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}