Chunpeng Wang, Weixiang Cui, He-wen Zhang, Xiaohui Qiu, Yuting Liu
In view of tight oil reservoirs with no natural productivity (tight sandstone and carbonate reservoirs with matrix permeability under overburden pressure of no more than 0.2mD (pore permeability less than 2mD)), a nanometer high efficient oil washing agent has been developed by combining nano-drop, high efficient oil washing surfactant and wettability reversal means, which can turn the disadvantage of the small pores and throats into advantage and realize fracturing effect enhancement by making use of the spontaneous imbibition. For the tight oil reservoir, large scale and high pumping rate multi-stage fracturing in horizontal wells and fracture diversion technique are recommended to smash the reservoirto create a fracture network of natural fractures and artificial fractures for oil and gas flow. The aim is to increase reservoir stimulation volume and the artificial fracture area. Meanwhile, nanometer high efficient oil washing agent is added in the fracturing fluid. By changing rock wettability, the oil-wet interface is turned water-wet, and the capillary force is changed from imbibition resistance to imbibition drive, boosting spontaneous imbibition. Therefore, the biobased solvent and surfactant can work in synergy to separate the oil film from pore and throat surface, realizing displacement of oil by water. Experimental data shows the application the nanometer oil displacement agent can enhance the oil displacement efficiency of core by12%. After fracturing, the well should be shut down for some time. The shut-down time should take the reservoir pressure and temperature, pore structure and connectivity and the imbibition capacity of the fracturing fluid etc into account, and can be worked out by spontaneous imbibition experiment and NMR etc to guide field operation. This technology has been used 10 well times in tight oil reservoirs in western China, including 3 well times of key exploration well stimulation, and 7 well times of old well repeated fracturing, all the treatments have achieved good effect. Among them, one well worth special note, this well had no production before fracturing, but obtained a high production of 42t a day after fracturing. During the shutdown of well, the fracturing fluid in the artificial fracture network can contact fully with micro-pores in the matrix and displace the oil in them through imbibition to the fracture system, then the oil can flow along the fracture network to the well bottom. The high efficient imbibition fracturing technology for tight oil reservoir is a revolution in fracturing. With fracturing fluid system and well shutdown different from traditional fracturing, this technology can enhance fracturing effect and more importantly oil recovery. This paper has great guidance and reference significance for engineers and researchers engaged in tight oil development.
{"title":"High Efficient Imbibition Fracturing for Tight Oil Reservoir","authors":"Chunpeng Wang, Weixiang Cui, He-wen Zhang, Xiaohui Qiu, Yuting Liu","doi":"10.2118/191274-MS","DOIUrl":"https://doi.org/10.2118/191274-MS","url":null,"abstract":"\u0000 In view of tight oil reservoirs with no natural productivity (tight sandstone and carbonate reservoirs with matrix permeability under overburden pressure of no more than 0.2mD (pore permeability less than 2mD)), a nanometer high efficient oil washing agent has been developed by combining nano-drop, high efficient oil washing surfactant and wettability reversal means, which can turn the disadvantage of the small pores and throats into advantage and realize fracturing effect enhancement by making use of the spontaneous imbibition.\u0000 For the tight oil reservoir, large scale and high pumping rate multi-stage fracturing in horizontal wells and fracture diversion technique are recommended to smash the reservoirto create a fracture network of natural fractures and artificial fractures for oil and gas flow. The aim is to increase reservoir stimulation volume and the artificial fracture area. Meanwhile, nanometer high efficient oil washing agent is added in the fracturing fluid. By changing rock wettability, the oil-wet interface is turned water-wet, and the capillary force is changed from imbibition resistance to imbibition drive, boosting spontaneous imbibition. Therefore, the biobased solvent and surfactant can work in synergy to separate the oil film from pore and throat surface, realizing displacement of oil by water. Experimental data shows the application the nanometer oil displacement agent can enhance the oil displacement efficiency of core by12%. After fracturing, the well should be shut down for some time. The shut-down time should take the reservoir pressure and temperature, pore structure and connectivity and the imbibition capacity of the fracturing fluid etc into account, and can be worked out by spontaneous imbibition experiment and NMR etc to guide field operation.\u0000 This technology has been used 10 well times in tight oil reservoirs in western China, including 3 well times of key exploration well stimulation, and 7 well times of old well repeated fracturing, all the treatments have achieved good effect. Among them, one well worth special note, this well had no production before fracturing, but obtained a high production of 42t a day after fracturing. During the shutdown of well, the fracturing fluid in the artificial fracture network can contact fully with micro-pores in the matrix and displace the oil in them through imbibition to the fracture system, then the oil can flow along the fracture network to the well bottom.\u0000 The high efficient imbibition fracturing technology for tight oil reservoir is a revolution in fracturing. With fracturing fluid system and well shutdown different from traditional fracturing, this technology can enhance fracturing effect and more importantly oil recovery. This paper has great guidance and reference significance for engineers and researchers engaged in tight oil development.","PeriodicalId":11006,"journal":{"name":"Day 3 Wed, June 27, 2018","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90771916","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}
Chaojie Zhao, Jun Li, Gong-hui Liu, Hui Zhang, Chao Wang, Kai Ren, Xin Zhang
Casing deformation turned out to be serious during hydraulic fracturing of shale gas wells in Weiyuan-Channing, where the ratio of casing deformation was more than 30%. Nevertheless, there were no such phenomenon in America and other shale gas producing areas. Why there were so many horizontal wells casing deformation in Weiyuan-Changning, China? There maybe kinds of factors. The authors mainly analyze the effect to casing deformation from operations factors during well drilling and completion, including dogleg angle, loss of cement sheath integrity and APD effect; as well as effect the geologic characteristics such as faults and natural fracture zones, lithologic interface, shale bedding. The results show that: Firstly, though the casing strength gradually decreased as the dogleg angle increasing, the casing collapsing strength drops off only 3.8% with average 2.7°/30m dogleg angle in the casing deformation zone, which showed that it can not lead casing deformation directly. Then, though the influence of temperature and loss of cement sheath integrity will significantly reduce the safety factor of the casing, it cannot be excluded that the local cement sheath can be always damaged after hydraulic fracturing, which suggested the APD effect was not the main factor leading to casing deformation. Finally, the original stress balance near wellbore can be destroyed during multistage hydraulic fracturing leading to non-uniform in-situ stress, which can active the fault, natural fractures, lithologic interface, shale bedding to slip. Therefore there were high probability of casing deformation in the formation with faults, natural fracture zones and strong heterogeneity. The above analysis can be used to explain why there is serious casing deformation in Weiyuan and Changning of China. Perforating far away from the point where casing deformation occurred easily and design the proper fracturing scheme can help us avoid casing deformation rather than simply raising steel grade and wall thickness of casing.
{"title":"The Casing Deformation During Shale Gas Hydraulic Fracturing: Why it is so Serious in Weiyuan-Changning, China?","authors":"Chaojie Zhao, Jun Li, Gong-hui Liu, Hui Zhang, Chao Wang, Kai Ren, Xin Zhang","doi":"10.2118/191273-MS","DOIUrl":"https://doi.org/10.2118/191273-MS","url":null,"abstract":"\u0000 Casing deformation turned out to be serious during hydraulic fracturing of shale gas wells in Weiyuan-Channing, where the ratio of casing deformation was more than 30%. Nevertheless, there were no such phenomenon in America and other shale gas producing areas. Why there were so many horizontal wells casing deformation in Weiyuan-Changning, China? There maybe kinds of factors.\u0000 The authors mainly analyze the effect to casing deformation from operations factors during well drilling and completion, including dogleg angle, loss of cement sheath integrity and APD effect; as well as effect the geologic characteristics such as faults and natural fracture zones, lithologic interface, shale bedding.\u0000 The results show that: Firstly, though the casing strength gradually decreased as the dogleg angle increasing, the casing collapsing strength drops off only 3.8% with average 2.7°/30m dogleg angle in the casing deformation zone, which showed that it can not lead casing deformation directly. Then, though the influence of temperature and loss of cement sheath integrity will significantly reduce the safety factor of the casing, it cannot be excluded that the local cement sheath can be always damaged after hydraulic fracturing, which suggested the APD effect was not the main factor leading to casing deformation. Finally, the original stress balance near wellbore can be destroyed during multistage hydraulic fracturing leading to non-uniform in-situ stress, which can active the fault, natural fractures, lithologic interface, shale bedding to slip. Therefore there were high probability of casing deformation in the formation with faults, natural fracture zones and strong heterogeneity.\u0000 The above analysis can be used to explain why there is serious casing deformation in Weiyuan and Changning of China. Perforating far away from the point where casing deformation occurred easily and design the proper fracturing scheme can help us avoid casing deformation rather than simply raising steel grade and wall thickness of casing.","PeriodicalId":11006,"journal":{"name":"Day 3 Wed, June 27, 2018","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75263301","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}
Forecasting future production and estimating ultimate recovery (EUR) in supertight reservoirs and shale plays has long been problematic. Developing a reliable and more accurate production forecast have always been a main goal of any petroleum operation. Effectively assessing the reservoir volume and well producing life is instrumental for creation of development scenarios and strategies to maximize the value to the company. Different models have been introduced and used for reserves estimation and production forecast of unconventional reservoirs. This work is intended to review and compare the methods and models currently used in the industry. Reserves estimation is a process that is constantly updated during the life of a reservoir. Its accuracy depends on the amount of data available and the method of forecast. Analytical models or rate transient analysis (RTA) methods are widely used for history matching and production forecast of unconventional reservoirs. Numerical simulation is also used for estimating ultimate recovery. Different relations have been introduced to model the rate/time behavior in unconventional plays as an alternative to the Arps’ decline curve analysis to address shortcomings when matching production history. Modified hyperbolic decline, power-law exponential decline (PLED), stretched-exponential decline (SEPD), Duong's method, and logistic-growth model (LGM) are developed for forecasting the production in shale reservoirs, but all are based on empirical observations of a particular scenario. In this study, different methods of history matching the production of hydraulically fractured unconventional reservoirs were investigated by forecasting future production and predicting EUR's to quantify the differences between them. The traditional Arps’ decline for low permeability reservoirs over-forecasts reserves. PLED, SEPD, LGM, and Duong's method were intended to represent the character of rate/time production data for the standard well completion in a multiple-fractured horizontal well in a shale play. These methods provide different forecasts as they have different equation forms. Unfortunately, all of them are not satisfactorily sufficient to forecast production for all unconventional reservoirs. The RTA analytical models required certain modifications of the reservoir and fracture parameters to provide optimistic EUR when compared to the numerical simulation. Different methods for forecasting unconventional well data have been reviewed and compared in this work based on the production forecast and EUR prediction. Field case production data has been used to reveal the accuracy of the models, the similarity of reserves estimation, and the relationship to the reservoir theory.
{"title":"EUR Prediction for Unconventional Reservoirs: State of the Art and Field Case","authors":"O. Mahmoud, M. Ibrahim, C. Pieprzica, S. Larsen","doi":"10.2118/191160-MS","DOIUrl":"https://doi.org/10.2118/191160-MS","url":null,"abstract":"\u0000 Forecasting future production and estimating ultimate recovery (EUR) in supertight reservoirs and shale plays has long been problematic. Developing a reliable and more accurate production forecast have always been a main goal of any petroleum operation. Effectively assessing the reservoir volume and well producing life is instrumental for creation of development scenarios and strategies to maximize the value to the company. Different models have been introduced and used for reserves estimation and production forecast of unconventional reservoirs. This work is intended to review and compare the methods and models currently used in the industry.\u0000 Reserves estimation is a process that is constantly updated during the life of a reservoir. Its accuracy depends on the amount of data available and the method of forecast. Analytical models or rate transient analysis (RTA) methods are widely used for history matching and production forecast of unconventional reservoirs. Numerical simulation is also used for estimating ultimate recovery. Different relations have been introduced to model the rate/time behavior in unconventional plays as an alternative to the Arps’ decline curve analysis to address shortcomings when matching production history. Modified hyperbolic decline, power-law exponential decline (PLED), stretched-exponential decline (SEPD), Duong's method, and logistic-growth model (LGM) are developed for forecasting the production in shale reservoirs, but all are based on empirical observations of a particular scenario.\u0000 In this study, different methods of history matching the production of hydraulically fractured unconventional reservoirs were investigated by forecasting future production and predicting EUR's to quantify the differences between them. The traditional Arps’ decline for low permeability reservoirs over-forecasts reserves. PLED, SEPD, LGM, and Duong's method were intended to represent the character of rate/time production data for the standard well completion in a multiple-fractured horizontal well in a shale play. These methods provide different forecasts as they have different equation forms. Unfortunately, all of them are not satisfactorily sufficient to forecast production for all unconventional reservoirs. The RTA analytical models required certain modifications of the reservoir and fracture parameters to provide optimistic EUR when compared to the numerical simulation.\u0000 Different methods for forecasting unconventional well data have been reviewed and compared in this work based on the production forecast and EUR prediction. Field case production data has been used to reveal the accuracy of the models, the similarity of reserves estimation, and the relationship to the reservoir theory.","PeriodicalId":11006,"journal":{"name":"Day 3 Wed, June 27, 2018","volume":"34 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79785551","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}
Royalty Lease Evaluation (RLE) distillation analysis was performed on six hundred (600) wells in Petrotrin's Soldado acreage. This data has been traditionally generated for use by Petrotrin's refinery to determine if the crude oil feedstock is compatible to the refinery configuration or if the crude oil could cause yield, quality and production problems. These made for refinery reports have become part of Petrotrin's legacy data. The authors decided to examine this dormant dataset to ascertain what hidden stories it may tell about the oilfields from which they came. In this investigation no data is generated, but an existing and dormant dataset will be analysed. Several components in a RLE distillation report on crude oil samples will be observed for trends, patterns and relationships. Ternary diagrams and cross-plots will be employed. Specific geochemical revelations from the RLE data will be validated by comparison to conventional gas chromatography data. This investigation will illustrate how evaporative fractionation, which is a later charge of light hydrocarbons mixing with an emplaced biodegraded oil is evidenced by a phenomenon called the" Gas Oil Anomaly", seen in the RLE data. Essentially this is the absence of any gas oil fraction combined with the presence of light hydrocarbons in the distillation data. It will also be demonstrated that presence of the later charge of light hydrocarbons has been the key factor in the prolific production from the Soldado reservoirs. Additional analysis of the light oil and gas oil fractions of a crude oil will reveal properties and characteristics that suggest there were different sources for both the originally emplaced oils and the later charge of light hydrocarbons. The data also shows that due to the evaporative fractionation phenomenon there is no correlation with API Gravity, oil viscosity, Sulphur content and depth of the reservoirs in Soldado. It will also be demonstrated that the data can be used as a qualitative tool leading to exploration plays in the Soldado acreage. Explorationists at Petrotrin will find the results of this investigation to be both useful and provocative as it directs their attention to specific Trinmar Soldado oilfields as deep exploration play areas in a manner that traditional geochemical analyses have not been able to. It also allows the practioners in the Petrotrin Soldado acreage to better understand the productivity and complex fluid distributions in the Soldado reservoirs.
{"title":"The Geochemistry and Exploration Plays Hidden in Royalty Lease Evaluation Distillation Data of Trinmar Oils","authors":"S. Paul, C. Archie, N. Gallai-Ragobar","doi":"10.2118/191267-MS","DOIUrl":"https://doi.org/10.2118/191267-MS","url":null,"abstract":"\u0000 Royalty Lease Evaluation (RLE) distillation analysis was performed on six hundred (600) wells in Petrotrin's Soldado acreage. This data has been traditionally generated for use by Petrotrin's refinery to determine if the crude oil feedstock is compatible to the refinery configuration or if the crude oil could cause yield, quality and production problems. These made for refinery reports have become part of Petrotrin's legacy data. The authors decided to examine this dormant dataset to ascertain what hidden stories it may tell about the oilfields from which they came.\u0000 In this investigation no data is generated, but an existing and dormant dataset will be analysed. Several components in a RLE distillation report on crude oil samples will be observed for trends, patterns and relationships. Ternary diagrams and cross-plots will be employed. Specific geochemical revelations from the RLE data will be validated by comparison to conventional gas chromatography data.\u0000 This investigation will illustrate how evaporative fractionation, which is a later charge of light hydrocarbons mixing with an emplaced biodegraded oil is evidenced by a phenomenon called the\" Gas Oil Anomaly\", seen in the RLE data. Essentially this is the absence of any gas oil fraction combined with the presence of light hydrocarbons in the distillation data. It will also be demonstrated that presence of the later charge of light hydrocarbons has been the key factor in the prolific production from the Soldado reservoirs.\u0000 Additional analysis of the light oil and gas oil fractions of a crude oil will reveal properties and characteristics that suggest there were different sources for both the originally emplaced oils and the later charge of light hydrocarbons. The data also shows that due to the evaporative fractionation phenomenon there is no correlation with API Gravity, oil viscosity, Sulphur content and depth of the reservoirs in Soldado. It will also be demonstrated that the data can be used as a qualitative tool leading to exploration plays in the Soldado acreage.\u0000 Explorationists at Petrotrin will find the results of this investigation to be both useful and provocative as it directs their attention to specific Trinmar Soldado oilfields as deep exploration play areas in a manner that traditional geochemical analyses have not been able to. It also allows the practioners in the Petrotrin Soldado acreage to better understand the productivity and complex fluid distributions in the Soldado reservoirs.","PeriodicalId":11006,"journal":{"name":"Day 3 Wed, June 27, 2018","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77502660","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}
Guangyue Liang, Shangqi Liu, Y. Liu, Yanyan Luo, B. Han, Jixin Huang, Yu Bao
Steam assisted gravity drainage (SAGD) process is widely used in super heavy oil and oil sands projects. These projects generally have higher steam to oil ratio and poor economy, partly because un-uniform steam chamber along the horizontal section forms and it is hard to adjust, affecting by reservoir heterogeneity including muddy interlayer and thief zones. Therefore, it is desirable to explore realistic and promising technology measures for SAGD projects at low oil price. In this paper, almost all the technology measures for SAGD projects were extensively and deeply investigated in terms of domestic and foreign reports, literatures and on-site experiences. The available research subjects include Xinjiang Fengcheng and Liaohe super heavy oil projects in China as well as ten oil sands project attached to eight corporations in Canada. Better yet, numerous statistics about technology application are reviewed well-by-well, and field application effects for some technologies were verified by deliberate numerical simulation. Many realistic and enforceable technology measures were systematically analyzed and recommended. Single or multiple stage dilation start-up process assisted by waste water or polymer injection enhanced start-up process significantly. Infilling well pairs or wedge well, and sidetracking horizontal well or fishbone well effectively tapped the unswept remaining oil by steam. The other technologies further improved steam chamber conformance including non-condensable gas co-injection, ICD/FCD technology, differentiated operating pressure strategy, nitrogen plus dispersant foam profile control and other remedial measures, etc. Besides, the present situation and foreground application were summarized and evaluated for several promising new technologies to be studied such as screening low cost mixed solvent to increase solvent recovery, warm solvent gravity drainage (Nsolv) process and in-situ upgrading process assisted by electrical heater or catalytic modification to reduce the capital cost of surface facility, etc. The paper contains some previously unpublished data of practical experiences, and the findings of this investigation add to the knowledge base information related to improving the SAGD performance and economy of super heavy oil or oil sands projects.
{"title":"Realistic and Promising Technology Measures for SAGD Projects at Low Oil Price","authors":"Guangyue Liang, Shangqi Liu, Y. Liu, Yanyan Luo, B. Han, Jixin Huang, Yu Bao","doi":"10.2118/191266-MS","DOIUrl":"https://doi.org/10.2118/191266-MS","url":null,"abstract":"\u0000 Steam assisted gravity drainage (SAGD) process is widely used in super heavy oil and oil sands projects. These projects generally have higher steam to oil ratio and poor economy, partly because un-uniform steam chamber along the horizontal section forms and it is hard to adjust, affecting by reservoir heterogeneity including muddy interlayer and thief zones. Therefore, it is desirable to explore realistic and promising technology measures for SAGD projects at low oil price.\u0000 In this paper, almost all the technology measures for SAGD projects were extensively and deeply investigated in terms of domestic and foreign reports, literatures and on-site experiences. The available research subjects include Xinjiang Fengcheng and Liaohe super heavy oil projects in China as well as ten oil sands project attached to eight corporations in Canada. Better yet, numerous statistics about technology application are reviewed well-by-well, and field application effects for some technologies were verified by deliberate numerical simulation.\u0000 Many realistic and enforceable technology measures were systematically analyzed and recommended. Single or multiple stage dilation start-up process assisted by waste water or polymer injection enhanced start-up process significantly. Infilling well pairs or wedge well, and sidetracking horizontal well or fishbone well effectively tapped the unswept remaining oil by steam. The other technologies further improved steam chamber conformance including non-condensable gas co-injection, ICD/FCD technology, differentiated operating pressure strategy, nitrogen plus dispersant foam profile control and other remedial measures, etc. Besides, the present situation and foreground application were summarized and evaluated for several promising new technologies to be studied such as screening low cost mixed solvent to increase solvent recovery, warm solvent gravity drainage (Nsolv) process and in-situ upgrading process assisted by electrical heater or catalytic modification to reduce the capital cost of surface facility, etc.\u0000 The paper contains some previously unpublished data of practical experiences, and the findings of this investigation add to the knowledge base information related to improving the SAGD performance and economy of super heavy oil or oil sands projects.","PeriodicalId":11006,"journal":{"name":"Day 3 Wed, June 27, 2018","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84560491","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}
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