Day 1 Tue, January 11, 2022最新文献

{"title":"A Novel Approach to Reservoir Simulation of Hydraulic Fractures: Performance Improvement Using Pseudo Well Connections","authors":"Aamir Lokhandwala, V. Joshi, A. Dutt","doi":"10.2118/205237-ms","DOIUrl":"https://doi.org/10.2118/205237-ms","url":null,"abstract":"\u0000 Reservoir simulation is used in most modern reservoir studies to predict future production of oil and gas, and to plan the development of the reservoir. The number of hydraulically fractured wells has risen drastically in recent years due to the increase in production in unconventional reservoirs. Gone are the days of using simple analytic techniques to forecast the production of a hydraulic fracture in a vertical well, and the need to be able to model multiple hydraulic fractures in many stages over long horizontals is now a common practice. The type of simulation approach chosen depends on many factors and is study specific. Pseudo well connection approach was preferred in the current case.\u0000 Due to the nature of the reservoir simulation problem, a decision needs to be made to determine which hydraulic fracture modeling method might be most suitable for any given study. To do this, a selection of methods is chosen based on what is available at hand, and what is commonly used in various reservoir simulation software packages. The pseudo well connection method, which models hydraulic fractures as uniform conductivity rectangular fractures was utilized for a field of interest referred to as Field A in this paper. Such an assumption of the nature of the hydraulic fracture is common in most modern tools.\u0000 Field A is a low permeability (0.01md-0.1md), tight (8% to 12% porosity) gas-condensate (API ~51deg and CGR~65 stb/mmscf) reservoir at ~3000m depth. Being structurally complex, it has a large number of erosional features and pinch-outs. The pseudo well connection approach was found to be efficient both terms of replicating data of Field A for a 10 year period while drastically reducing simulation runtime for the subsequent 10 year-period too. It helped the subsurface team to test multiple scenarios in a limited time-frame leading to improved project management.","PeriodicalId":11087,"journal":{"name":"Day 1 Tue, January 11, 2022","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79942947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterize Fracture Development Through Strain Rate Measurements by Distributed Acoustic Sensor DAS","authors":"Jin Tang, D. Zhu","doi":"10.2118/205267-ms","DOIUrl":"https://doi.org/10.2118/205267-ms","url":null,"abstract":"\u0000 In multistage hydraulic fracturing treatments, the combination of extreme large-scale pumping (high rate and volume) and the high heterogeneity of the formation (because of large contact area) normally results in complex fracture growth that cannot be simply modeled with conventional fracture models. Lack of understanding of the fracturing mechanism makes it difficult to design and optimize hydraulic fracturing treatments. Many monitoring, testing and diagnosis technologies have been applied in the field to describe hydraulic fracture development. Strain rate measured by distributed acoustic sensor (DAS) is one of the tools for fracture monitoring in complex completion scenarios. DAS measures far-field strain rate that can be of assistance for fracture characterization, cross-well fracture interference identification, and well stimulation efficiency evaluation. Many field applications have shown DAS responses on observation wells or surrounding producers when a well in the vicinity is fractured. Modeling and interpreting DAS strain rate responses can help quantitatively map fracture propagation.\u0000 In this work, a methodology is developed to generate the simulated strain-rate responds to assumed fracture systems. The physical domain contains a treated well that the generate strain variation in the domain because of fracturing, and an observation well that has fiber-optic sensor installed along it to measure the strain rate responses to the fracture propagation. Instead of using a complex fracture model to forward simulate fracture propagation, this work starts from a simple 2D fracture propagation model to provide hypothetical fracture geometries in a relatively reasonable and acceptable range for both single fracture case and multiple fracture case. Displacement discontinuity method (DDM) is formulated to simulate rock deformation and strain rate responds on fiber-optic sensors. At each time step, fracture propagation is first allowed, then stress, displacement and strain field are estimated as the fracture approaches to the observation well. Afterward, the strain rate is calculated as fracture growth to generate patterns as fracture approaching. Extended simulation is conducted to monitor fracture propagation and strain rate responses. The patterns of strain rate responses can be used to recognize fracture development.\u0000 Examples of strain rate responses for different fracturing conditions are presented in this paper. The relationship of injection rate distribution and strain rate responses is investigated to show the potential of using DAS measurements to diagnose multistage hydraulic fracturing treatments.","PeriodicalId":11087,"journal":{"name":"Day 1 Tue, January 11, 2022","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90110407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Application of Integrated Far-Field Diversion Technology in Multistage Acid-Fracturing: Lesson Learnings from Unconventional Field North Kuwait","authors":"A. Al-Enezi, Mohammed Al-Othman, Mishari Al-Shtail, Yousef Al-Sadeeqi, K. Bhatia, A. Alboueshi, Amr Abdelbaky","doi":"10.2118/205265-ms","DOIUrl":"https://doi.org/10.2118/205265-ms","url":null,"abstract":"\u0000 The unconventional Bahrah field is a high potential field which poses several challenges in terms of hydrocarbon flow assurance through highly heterogeneous tight carbonate intervals with poor reservoir quality and curtailed mobility. Due to this, the field development strategies have prioritized well completion using horizontal acid fracturing technology over vertical wells. During fracturing, the acid system tends to form highly conductive channels in the formation. Most of the fluid will flow into the path of least resistance leaving large portions of the formation untreated. As a result, the fracturing treatment options dwindle significantly, thus reservoir stimulation results are not optimum in each stage.\u0000 Achieving complete wellbore coverage is a challenge for any acid frac treatment performed in long lateral with variations in reservoir characteristics. The multistage acid fracturing using Integrated Far-field Diversion (IFD) is performed using selective openhole completion, enabling mechanical annular segmentation of the wellbore using swellable packers and sliding sleeves. The mechanical as well as chemical diversion in IFD methodology is highly important to the overall stimulation success. The technique includes pumping multiple self-degrading particle sizes, considering the openhole annular space and wide presence of natural fractures, followed by in-situ HCL based crosslinked system employed for improving individual stage targets. A biomodal strategy is employed wherein larger particles are supplemented with smaller that can bridge pore throats of the larger particles and have the desired property of rigidity and develop a level of suppleness once exposed to reservoir conditions. The IFD diversion shifts the fracture to unstimulated areas to create complex fractures that increase reservoir contact volume and improving overall conductivity.\u0000 This paper examines IFD in acid fracturing and describes the crucial diversion strategy. Unlike available diverters used in other fields, the particulates are unaffected at low pH values and in live acids. Proper agent selection and combination with in-situ crosslink acid effectively plug the fracture generated previously and generate pressure high enough to initiate another fracture for further ramification. The optimization and designing of the IFD diversion in each stage plays a key role and has helped to effectively plug fractures and realize segmentation. Concentration of diversion agents, volume of fluid system and open-hole stage length sensitivity plays vital role for the success of this treatment.\u0000 The application of IFD methodology is tuned as fit-for-purpose to address the unique challenges of well operations, formation technical difficulties, high-stakes economics, and untapped high potential from this unconventional reservoir. A direct result of this acid fracturing treatment is that the post-operation data showed high contribution of all fractured zones along the section in sustain","PeriodicalId":11087,"journal":{"name":"Day 1 Tue, January 11, 2022","volume":"151 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77291751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Supervised Learning Predictive Models for Automated Fracturing Treatment Design: A Workflow Based on Algorithm Comparison and Multiphysics Model Validation","authors":"AbdulMuqtadir Khan, Abdullah Binziad, Abdullah Al Subaii, T. Alqarni, Mohamed Yassine Jelassi, Asim Najmi","doi":"10.2118/205310-ms","DOIUrl":"https://doi.org/10.2118/205310-ms","url":null,"abstract":"\u0000 Diagnostic pumping techniques are used routinely in proppant fracturing design. The pumping process can be time consuming; however, it yields technical confidence in treatment and productivity optimization. Recent developments in data analytics and machine learning can aid in shortening operational workflows and enhance project economics. Supervised learning was applied to an existing database to streamline the process and affect the design framework.\u0000 Five classification algorithms were used for this study. The database was constructed through heterogeneous reservoir plays from the injection/falloff outputs. The algorithms used were support vector machine, decision tree, random forest, multinomial, and XGBoost. The number of classes was sensitized to establish a balance between model accuracy and prediction granularity. Fifteen cases were developed for a comprehensive comparison. A complete machine learning framework was constructed to work through each case set along with hyperparameter tuning to maximize accuracy. After the model was finalized, an extensive field validation workflow was deployed.\u0000 The target outputs selected for the model were crosslinked fluid efficiency, total proppant mass, and maximum proppant concentration. The unsupervised clustering technique with t-SNE algorithm that was used first lacked accuracy. Supervised classification models showed better predictions. Cross-validation techniques showed an increasing trend of prediction accuracy. Feature selection was done using one-variable-at-a-time (OVAT) and a simple feature correlation study. Because the number of features and the dataset size were small, no features were eliminated from the final model building. Accuracy and F1 score calculations were used from the confusion matrix for evaluation, XGBoost showed excellent results with an accuracy of 74 to 95% for the output parameters. Fluid efficiency was categorized into three classes and yielded an accuracy of 96%. Proppant concentration and proppant mass predictions showed 77% and 86% accuracy, respectively, for the six-class case. The combination of high accuracy and fine granularity confirmed the potential application of machine learning models. The ratio of training to testing (holdout) across all cases ranged from 80:20 to 70:30. Model validations were done through an inverse problem of predicting and matching the fracture geometry and treatment pressures from the machine learning model design and the actual net pressure match. The simulations were conducted using advanced multiphysics simulations.\u0000 The advantages of this innovative design approach showed four areas of improvement: reduction in polymer consumption by 30%, reduction of the flowback time by 25%, reduction of water usage by 30%, and enhanced operational efficiency by 60 to 65%.","PeriodicalId":11087,"journal":{"name":"Day 1 Tue, January 11, 2022","volume":"17 17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88807680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First Successful Application of Multi-Stage Proppant Fracturing on Horizontal Well in Carbonate Reservoirs in Iraq","authors":"D. Zhu, M. Cui, Yandong Chen, Yongli Wang, Yun-hong Ding, C. Xiong, C. Liang, Fei Yao, Xiaoyong Wang, Wenxin Cai, Yanhui He, Zongfa Ling, Dayong Wang","doi":"10.2118/205281-ms","DOIUrl":"https://doi.org/10.2118/205281-ms","url":null,"abstract":"\u0000 The carbonate reservoir S is a giant limestone reservoir in H Oilfield, Iraq. Although the reserves account for 25%, the production contribution is only 0.4% to the total oilfield production due to poor petrophysical properties. Accordingly, the first proppant fracturing on vertical well was successfully executed in December 2016, which has already achieved a steady production period over than 3 years. In order to further improve the productivity, the first multi-stage proppant fracturing(MSPF) on horizontal well(SH01X) was successfully applied in November 2019, a technique which is rarely reported for porous limestone reservoir in the Middle East.\u0000 Proppant fracturing in carbonate reservoirs is a technique difficulty worldwide, especially this is a lack of experiences in the Middle East. To ensure the success of this campaign, a holistic technical study including geology evaluation, reservoir performance analysis, drilling trajectory design, completion and fracturing technique design have been carried out based on principle of \"geology-engineering integration\". This paper will present a comprehensive illustration including treatment design (main completion-fracturing technique, total scale, fracturing fluid, proppant), job execution (mini-frac, main-frac) and post-frac production performance for this successful campaign.\u0000 True vertical depth (TVD) of Well SH01X is 2720 m and the horizontal section length is 811 m. Based on the main technique of multi-stage proppant fracturing with open hole packers and sliding sleeves, totally 3784.3 m3 fracturing fluid and 452 m3 proppant were pumped in 8 stages. The test production was 3214 BOPD (choke size: 40/64\", wellhead pressure: 970 psi). A historical breakthrough in the productivity of S reservoir has been achieved by the campaign. The post-frac evaluation shows that the treatment parameters are consistent with the design. The connectivity between artificial fractures and formation is greatly improved, and the stimulation effect is significant. Currently the \"production under controlled pressure\" mode has been executed and the stable production under stimulation target rate has been maintained. The systematic \"geology-engineering integration\" workflow is of significance to the success of the treatment as well as the stimulation effect.\u0000 MSPF is planned to be a game-changing technique to develop the huge reserves of S reservoir. The experience gained from this case could provide theoretical as well as practical references for similar reservoirs in the Middle East.","PeriodicalId":11087,"journal":{"name":"Day 1 Tue, January 11, 2022","volume":"101 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76262465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"From Technical Evolution to Production Performance: A Technical Review of 700 Wells Over 8 Years in the South Sulige Tight Gas Field","authors":"Dong Wang, Yiwen Dong, Shengfang Yang, Joel Rignol, Qianqian Wang, Yuan Liu, Yaolan Liu, Liang Zhao, Weikan Wang, P. Loh, P. Enkababian","doi":"10.2118/205262-ms","DOIUrl":"https://doi.org/10.2118/205262-ms","url":null,"abstract":"\u0000 Unlike many unconventional resources that demonstrate a high level of heterogeneity, conventional tight gas formations often perform consistently according to reservoir quality and the applied completion technology. Technical review over a long period may reveal the proper correlation between reservoir quality, completion technology, and well performance. For many parts of the world where conventional tight gas resources still dominate, the learnings from a review can be adapted to improve the performance of reservoirs with similar features.\u0000 South Sulige Operating Company (SSOC), a joint venture between PetroChina and Total, has been operating in the Ordos basin for tight gas since 2011. The reservoir is known to have low porosity, low permeability, and low reservoir pressure, and requires multistage completion and fracturing to achieve economic production.\u0000 Over the last 8 years, there has been a clear technical evolution in South Sulige field, as a better understanding of the reservoir, improvement of the completion deployment, optimized fracturing design, and upgraded flowback strategy have led to the continuous improvement of results in this field. Pad drilling of deviated boreholes, multistage completions with sliding sleeve systems, hybrid gel-fracturing, and immediate flowback practices, gradually proved to be the most effective way to deliver the reservoir's potential.\u0000 Using the absolute open-flow (AOF) during testing phase for comparative assessment from South Sulige field, we can see that in 2012 this number was 126 thousand std m3/d in 2012, and by 2018 this number had increased to 304 thousand std m3/d, representing a 143% incremental increase. Thus, technical evolution has been proved to bring production improvement over time. Currently, South Sulige field not only outperforms offset blocks but also remains the top performer among the fields in the Ordos basin. The drilling and completion practices from SSOC may be well suited to similar reservoirs and fields in the future.","PeriodicalId":11087,"journal":{"name":"Day 1 Tue, January 11, 2022","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81766690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Controlled Frac Height Growth Technique to Avoid Contacting Water-Bearing Layer","authors":"Hashem Al-Obaid, S. Asel, Jon E. Hansen, Rio Wijaya","doi":"10.2118/205278-ms","DOIUrl":"https://doi.org/10.2118/205278-ms","url":null,"abstract":"\u0000 Many techniques have been used to model, diagnose and detect fracture dimension and propagation during hydraulic fracturing. Diagnosing fracture dimension growth vs time is of paramount importance to reach the desired geometry to maximize hydrocarbon production potential and prevent contacting undesired fluid zones. The study presented here describes a technique implemented to control vertical fracture growth in a tight sandstone formation being stimulated near a water zone. This gas well was completed vertically as openhole with Multi- Stage Fracturing (MSF).\u0000 Pre-Fracturing diagnostic tests in combination with high-resolution temperature logs provided evidence of vertical fracture height growth downward toward water zone. Pre-fracturing flowback indicated water presence that was confirmed by lab test. Several actions were taken to mitigate fracture vertical growth during the placement of main treatment. An artificial barrier with proppant was placed in the lower zone of the reservoir before main fracturing execution. The rate and viscosity of fracturing fluids were also adjusted to control the net pressure aiming to enhance fracture length into the reservoir.\u0000 The redesigned proppant fracturing job was placed into the formation as planned. Production results showed the effectiveness of the artificial lower barrier placed to prevent fracture vertical growth down into the water zone. Noise log consists of Sonic Noise Log (SNL) and High Precision Temperature (HPT) was performed. The log analysis indicated that two major fractures were initiated away from water-bearing zone with minimum water production. Additionally, in- situ minimum stress profile indicated no enough contrast between layers to help confine fracture into the targeted reservoir. Commercial gas production was achieved after applying this stimulation technique while keeping water production rate controlled within the desired range.\u0000 The approach described in this paper to optimize gas production in tight formation with nearby water contact during hydraulic fracturing treatments has been applied with a significant improvement in well production. This will serve as reference for future intervention under same challenging completion conditions.","PeriodicalId":11087,"journal":{"name":"Day 1 Tue, January 11, 2022","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91151610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Performance of 15 Years of Hydraulic Fracturing of Oil Wells in South of Oman","authors":"M. Molenaar, A. Al-Ghaithi, S. Kindi, Fahad Alawi","doi":"10.2118/205236-ms","DOIUrl":"https://doi.org/10.2118/205236-ms","url":null,"abstract":"\u0000 The first application of Hydraulic Fracturing in the South Oman started in 2000 to enhance water disposal wells. In 2004 the first oil wells were frac'ed. Although the technology was deployed many times, it never grew into a conventional practice. From 2004 to 2017 on average 5 Oil Wells were hydraulically fractured on yearly basis.\u0000 In November 2017, a Hydraulic Fracturing Maturation & Expansion Workshop was conducted with the vision of growing the application by applying new frac concepts. A focused effort was initiated to drastically reduce cost, and simultaneously increase the scope by executing larger frac campaigns. The first hydraulic fracturing campaign introducing the frac new concepts, started end 2018 and a rapid growth from 5 wells per year to 45 wells per year was anticipated in the next three years.\u0000 This large growth of scope relied on a steady supply of frac candidates and needed to be supported by screening and selecting processes that are fit for purpose in finding candidates. Although more than a hundred wells had already been frac'ed wells, selection of the most appropriate wells for stimulation was and remains one of the greatest challenges.\u0000 A frac performance database was created for over 100 wells that had been hydraulically fracture stimulated to date. Recognizing that the frac performance depends on many variables ranging from subsurface properties to surface execution of the frac job, the size of the dataset proved to be too small to find correlations using sophisticated multivariable regression methods. Instead, the dataset was analyzed through careful investigation and evaluation of each frac job. In this paper the net oil gain will be used as the key success criteria i.e., value driver to demonstrates how effective the frac is achieving its business objective. Some 40% of the producers had been producing from the same zone before the hydraulic fracture stimulation. This provided the opportunity to understand the efficiency of the stimulation in terms of the \"stimulation ratio\" i.e., measuring the net oil gain.\u0000 This paper will focus on investigating the suitability of frac'ing the reservoir based on the initial production variables; Gross Rate and BS&W. Also, this paper will discuss benefits and impacts of Hoist versus Coiled-Tubing clean-out on the frac delivery process and compare the frac performance.\u0000 To date, the project demonstrated that hydraulic fracturing at low cost, can be applied as a viable development concept for producing oil wells, with the potential unlock additional and new reserves. Significant folds in production increase are possible from 2x to 7x.","PeriodicalId":11087,"journal":{"name":"Day 1 Tue, January 11, 2022","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89662716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of Wormhole Profiles on Carbonate Rocks Using Emulsified and Single-Phase Retarded Acids","authors":"Norah W. Aljuryyed, Abdullah Al Moajil, S. Çalışkan, S. Alghamdi","doi":"10.2118/205285-ms","DOIUrl":"https://doi.org/10.2118/205285-ms","url":null,"abstract":"\u0000 Acid retardation through emulsification is commonly used in reservoir stimulation operations, however, emulsified acid are viscous fluids, thus require additional equipment at field for preparation and pumping requirements. Mixture of HCl with organic acids and/or chemical retarders have been used developed to retard acid reaction with carbonate, however, lower dissolving power. Development of low viscosity and high dissolving retarded acid recipes (e.g., equivalent to 15-26 wt.% HCl) addresses the drawbacks of emulsified acids and HCl acid mixtures with weaker organic acids. The objective of this study is to compare wormhole profile generated as a result of injecting acids in Indian limestone cores using 28 wt.% emulsified acid and single-phase retarded acids at comparable dissolving power at 200 and 300°F. Coreflood analysis testing was conducted using Indiana limestone core plugs to assess the pore volume profile of retarded acid at temperatures of 200 and 300° F. This test is supported by Computed Tomography to evaluate the propagation behavior as a result of the fluid/rock reaction.\u0000 Wider wormholes were observed with 28 wt.% emulsified acid at 200°F when compared to test results conducted at 300°F. The optimum injection rate was 1 cm3/min at 200 and 300°F based on wormhole profile and examined flow rates. Generally, face-dissolution and wider wormholes were observed with emulsified acids, especially at 200°F. Narrower wormholes were formed as a result of injecting retarded acids into Indiana limestone cores compared to 28 wt.% emulsified acid. Breakthrough was not achieved with retarded acid recipe at 300°F and flow rates of 1 and 3 cm3/min, suggesting higher flow rates (e.g., > 3 cm3/min) are required for the retarded acid to be more effective at 300°F.","PeriodicalId":11087,"journal":{"name":"Day 1 Tue, January 11, 2022","volume":"112 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90390034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydraulic Fracturing to Successfully Exploit Depleted Gas Reserves: A Case History from the North Sea","authors":"M. Norris, M. Langford, C. Giraud, Reginald Stanley, Steve Ball","doi":"10.2118/205335-ms","DOIUrl":"https://doi.org/10.2118/205335-ms","url":null,"abstract":"\u0000 Hydraulic fracturing has been well established in the Southern North Sea (SNS) since the mid-1980s; however, it has typically been conducted as the final phase of development in new gas fields. One of these fields is Chiswick located in the Greater Markham area 90 miles offshore UK in 130 ft of water. Following an unsuccessful well repair of the multi-fractured horizontal well C4, it was decided to cost-effectively and expediently exploit the remaining pressure-depleted reserves near the toe via a single large fracture initiated from a deviated sidetrack wellbore designated C6. A deviated wellbore was chosen versus the original near-horizontal well to reduce well risk and costs and ultimately deliver an economic well.\u0000 Several key challenges were identified, and mitigating measures were put in place. Modular formation dynamics tester data from the sidetrack open hole indicated the reservoir pressure gradient had depleted to 0.23 to 0.25 psi/ft, raising concerns about the ability of the well to unload the fluid volumes associated with a large fracture treatment. Wellbore deviation and azimuth with the associated potential for near-wellbore tortuosity would drive a typically short perforation interval (i.e., 3 ft). However, a compromise to mitigate convergent pressure loss in depletion was required, and the perforation interval was therefore set at 14 ft with provision made for robust step-down tests (SDT) and multi-mesh sand slugs. To further offset any near-well convergence pressure drop during cleanup, an aggressive tip screenout (TSO) proppant schedule, including a high concentration tail-in (12 PPA) with an aggressive breaker schedule, was executed to fully develop propped hydraulic width.\u0000 Following formation breakdown and SDT to 40 bbl/min, the well went on near-instantaneous vacuum. Clearly, an extremely conductive feature had been created or contacted. However, upon use of a robust crosslinked gel formulation and 100-mesh sand, the bottomhole and positive surface pressure data allowed a suitable fracture design to be refined and placed with a large width, as evidenced by the extreme 2,309-psi net pressure development over that of the pad stage while placing 500,500 lbm of 16/30 resin-coated (RC) intermediate strength proppant (ISP) to 12 PPA. Although a lengthy nitrogen lift by coiled tubing (CT) was planned, the well cleanup response in fact allowed unaided hydrocarbon gas flow to surface within a short period. The well was then further beaned-up under well test conditions to a flow rate of approximately 26 MMscf/D under critical flowing conditions with a higher bottomhole flowing pressure than that of the original C4 well. Given the last producing rate of the original multiple fractured horizontal wellbore was 27 MMscf/D at a drawdown of 1,050 psi through two separate hydraulic fractures, then the outcome of this well was judged to be highly successful and at the limit of predrill expectations.\u0000 This case history explains and details t","PeriodicalId":11087,"journal":{"name":"Day 1 Tue, January 11, 2022","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77456522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}