Abstract:The field development practices at extra high water-cut stage demonstrated that the oil recovery can still be enhanced a lot by the following water-flooding even if the water-flood mode is not changed and the areal and vertical sweep efficiency are very high.This phenomenon can not be interpreted by the conventional theory recovery definition in which the theory recovery is defined as the product of displacement efficiency, areal sweep efficiency and vertical sweep efficiency. Moreover, it is difficult to theoretically give advice for further improving oil recovery at extra high water-cut stage based on the conventional comprehension and the definition of the recovery. The laboratory experiments proved that the sweep degree of microscopic pores, which are in the areal and vertical sweep scope, increased continuously besides the increment of the macroscopic areal and vertical sweep efficiency during the water-flood process. On one hand, the number of the swept pores increased continuously, on the other hand, the swept volume (swept scope) of the swept pores became greater too. The conventional definition of theory recovery can only characterize the relevance of areal and vertical sweep efficiency to recovery, and not sufficient to represent the sweep features of the rock pores. Therefore, the definition of pore sweep extent is presented, and then, it is used to deduce a new evaluation expression of the water-flooding recovery. It indicates that the increment of the pore sweep extent is the main factor for improving oil recovery at extra high water-cut stage.

Abstract:Focusing on the northwestern part of Yanan sag of Qiongdongnan basin, we studied the sedimentary characteristics of Yacheng formation in Oligocene mainly through composition, grain size and sedimentary structure analysis. Typical braided delta sedimentary system has been identified in Yacheng formation. The lithology of the braided delta system is characterized by coarse clastic rocks which contain several thin coal seams and marine authigenic minerals such as glauconite. The rocks have multiple grain size cumulative curves both characterized by tractive and gravity flow. Sedimentary structures include multiple beddings such as parallel, tidal, uniform beddings and climbing-ripple cross-lamination, and many erosion surfaces and deformations, reflecting the complex and changeable hydrodynamic condition. Assisted by the logging curve characteristics and previous works, we constructed the sedimentary model of the braided delta system. We suggest that the braided delta system of the Yacheng formation in the study area was formed in the setting of balance filling in the early forming stage of the basin and developed near the vanish end of the main fault of the half graben. The braided delta system mainly includes subfacies of braided delta plain and braided delta front, and the main source areas are the Hainan uplift and Yacheng heave. Coal seams of the braided delta system are high quality source rock, together with the coarse grain rocks, forming the favorable lithological assemblage, which is important to the formation of the Yacheng13-1 gas field.

Abstract:As one of the major exploration target zones, the Qianjiang formation contains abundant oil resources, but the study on hydrocarbon accumulation dynamic system is very weak, restricting the exploration progress. Under the direction of dynamic system of hydrocarbon migration and accumulation theory and method, the dynamic system for hydrocarbon migration and accumulation of the Qianjiang formation in the north of Qianjiang depression is identified and classified. On the basis of tectonic-edimentary cycle, and through the source-reservoir-seal assemblage, traverse distribution characteristics of uncompacted belt, oil and gas source and strata sealing property analysis, the Qianjiang formation in northern Qianjiang depression is divided into four dynamic hydrocarbon accumulation subsystems：lower self-source overpressure and semi-enclosed subsystemⅠ, lower mixed-source overpressure and semi-enclosed subsystem Ⅱ, middle mixed-source overpressure and semi-enclosed subsystem Ⅲ and upper allo-source constant pressure and semi-open subsystem Ⅳ.The accumulation model in the study area can be subdivided into several types such as internal-lateral migration-multistage accumulated model, compound source-vertical and lateral migration-multi-stage accumulated model and external source vertical and lateral migration-multi-stage accumulated model.

Abstract:In order to provide guidance for exploration activity in the Guantao formation of Raoyang sag, the authors utilize the detrital components and its changes in the plane, heavy mineral assemble, ZTR coefficient, the thickness of layer and distribution characteristics of sand to research the provenances of Guantao formation in Raoyang sag. The analysis result shows that the provenances are derived from the northeastern and the southwestern of the Raoyang sag. Both provenances are metamorphic area and meet together at Liulu area in the center of Raoyang sag. The northeastern provenances has lower composition maturity, it is feldspathic lithic sandstone area; the southwestern provenances has the higher composition maturity than northeastern provenances, it is lithic feldspar sandstone area; the area of Liulu where two sources meet together is feldspar sandstone area. With the control of provenances, the braid river sedimentary facies distribution is near provenance area, and the meandering river sedimentary facies distribution is far away from provenance area, moreover, the channel bar and point bar are favorability sand bodies, and the area of Liulu where two sources meet together is of favorability prospect. The study on the provenances has important significance for sedimentary facies, sand body distribution and prediction of favorable exploration areas.

Abstract:The Hongsanhanyihao and Niubiziliang area developed two provenance systems which controlled the fan delta and shallow lake sedimentary system in western Qaidam basin. By means of the core observation, the sandstone framework component character,the type of the heavy mineral and their assemblages features, several wells are joined together to compare the sand, and analyze the paleo-geographic settings of Lulehe formation in the Honganhanyihao and Niubiziliang area. The provenance system and sedimentary system are studied comprehensively. The results show that this area developed fan delta in the shallow lake which is controlled by the Hongsanhanyihao sedimentary provenance and the west valley of the Niubiziliang sedimentary provenance in the time of the Lulehe formation. The Hongsanhanyihao sedimentary provenance is consisted of three embranchments: firstly, Jiandingshan water system, which mainly flowed southwest into Jiandingshan area by the first high point of the Hongsanhanyihao, secondly, the Changweiliang water system, which mainly flowed south into Changweiliang area by the third high point of the Hongsanhanyihao, and thirdly, Jianbei water system, which mainly flowed southeast into the north of Jianshan area by the fifth high point of the Hongsanhanyihao. And, the west valley of the Niubiziliang sedimentary provenance mainly flowed southeast to the east of the Jianshan area.

Abstract:The tight reservoir in the eastern Sulige is influenced by multi-period sedimentary, diagenesis and structure. And, it has small space, strong anisotropism, complex pore structure and complicated log response. The paper analyzes the remaining gas in invaded zone and offers the contrast between the limit and assessment of gas-bearing formations, influenced by saturation of residual and remaining movable gas. The research presents lower differences of residual gas saturation and greater differences of remaining movable gas saturation in tight reservoir of classified petrophysical phase. So, the assessment of gas formations in classified petrophysical phase can be established based on lithology, physical property, logging curves and hydrocarbons response to remaining movable gas in different types of gassy formations. The re-evaluation in tight reservoir is made among 46 wells in the study region. It is recommended to add gas formation, bad gas formation and gas reservoir section to test, which is beneficial to tight reservoir to reach a high output.

Abstract:Based on the fine reservoir description achievements, we made a systematic summarization of hydrocarbon distribution features in Tongbomiao formation in Tanan sag, and analyzed its major controlling factors. The results show that the hydrocarbon distribution is extremely heterogeneous in different structure zones in Tanan sag. The west and central fracture burial hill belt and the structural transform zone in the middle secondary hollow are the very place of hydrocarbon enrichment and high-production, and its reservoir types mainly include fault block reservoir, fault anticlinal reservoir and fault-nose reservoir. The reserve abundance and oil-production capacity is lower in south and north trough in the middle secondary hollow, and its reservoir types mainly include fault block-stratigraphic oil reservoir, lithologic reservoir and unconformity barrier reservoir. Through the analysis of the main control factors shows that differential structural and sedimentary pattern of the different structure zones controls the formation and distribution of the various reservoir types, the discrepancy of the reservoir facies belt caused by sedimentary facies and diagenism facies determines the reservoir quality and then controls the reserve and productivity of oil, the different hydrocarbon transport system determines the hydrocarbon migration-accumulation rule and controls the formation of three kinds of hydrocarbon heterogeneous distribution models, including outside-source unconformity translocation fault controlling oil-enrichment model, within-source mixed translocation facies controlling oil-depletion model and near-source fault translocation fault controlling oil-enrichment model.

Abstract:Integrated with analysis of seismic data, drilling data and logging data, this paper divided the Paleocene Lingshui formation into four third order sequence and established the sequence framework of Paleocene Lingshui formation in Qiongdongnan basin by using the principle and methods of sequence stratigraphy, sedimentology and petroleum geology. On the basis of the sequence framework,we analyzed the spatial distribution characteristics of each sequence. The results indicate that the development and evolution of the four sequences are characterized with inheritance and cyclicity in vertical. The depocenter which was in the northwest in the early stage moved to the south later. And, it was in the northwest again in the late stage. The deposition range of the basin varied during different stages. Different sag is of different deposition evolution feature. The distribution of the sequence is mainly controlled by the depocenter.Tectonic activity obviously controls the distribution of sedimentary strata. The thickness of the sequence is thick near the boundary fault in the each sag and becomes thinner in the gentle slope. Tectonic and sea level are the main factors controlling the development of the sequence.

Abstract:Abnormally high formation pressure commonly exists in formation upper Es4, lower Es3, middle Es3 source rocks of Paleogene, Lijin subsag, Shengli oilfield. The formation mechanisms of abnormally high pore pressure in Paleogene source rocks are analyzed herein. Also, the pore pressure profiles of 80 drilled exploration wells in this subsag are established by Comprehensive Explanation Method. Moreover, the pore pressure distribution features of source rocks are researched through drawing contour maps of formation upper Es4, lower Es3, middle Es3, respectively. The Comprehensive Explanation Method has a high precision in calculating abnormally high pore pressure of source rocks in Lijin subsag formed with combined action of under-compaction and hydrocarbon generation. The abnormally high pore pressure of Paleogene source rocks in Lijin subsag distributes with a trend from northeast to southwest.The pore pressure is high or ultra-high in the central region of Lijin subsag, and decreases to a normal level in the periphery area. The abnormally high formation pressure in the source rocks of Lijin subsag is the main force of hydrocarbon expulsion from the central subsag to the periphery area.

Abstract:Analysis and test data of reservoir water of Huzhuangji-Qingzuji oilfield in western Dongpu depression shows that the water type is CaCl2 and is of high salinity. The chemical composition mainly includes C1- and Na+ and controlled the spatial distribution of the reservoir water’s composition. This is caused by saline lake sediment environment. Due to the water-rock interaction, the ions, such as Ca2+, Mg2+, CO32-, SO42-, have less correlation with salinity. Two underground hydrodynamic cycles have developed corresponding to Paleogene and Neogene- Quaternary respectively. The first cycle could be divided into two stages: ①clay compacting water centrifugal flow stage during Shahejie-Dongying subsidence; and ②atmospheric water filtration centripetal flow stage during Dongying uplift. The clay compacting water centrifugal hydrodynamic is positive to hydrocarbon accumulation, moreover, and the atmospheric water filtration centripetal hydrodynamic re-build reservoirs formed in western slope of Dongpu depression. The favorite belt for oil accumulation is from the intersection area of the two different hydrodynamic stages to the second terrace of the depression. The first terrace is formed in Neogene-Quaternary, which is of stagnant hydrodynamic conditions, and the self-generating and self-preserving reservoirs could develop there.

Abstract:The magmatism can affect reservoir characteristics, and it can guide the oil and gas exploration. Through the microscopic identification and geochemical analysis, we studied the intrusive rocks in the Bachu-Yijianfang area. The composition of gabbro and diabase in the Bachu-Yijianfang area shows that w(SiO2) 39.91%-44.62%,w(K2O+Na2O) 3.04%-3.95%, and w(Na2O)/w(K2O) 2.32-2.8;the rock is rich in Ba with a negative Sr anomaly;ΣREE (106.72-158.15)×10-6, LREE/HREE 5.44-5.89, LaN/YbN 5.124-5.442, and δEu 1.091-1.237. The chemical characteristics and tectonic diagram show that the rock occurs in a typical within-plate environment,and belongs to the Na-rich alkaline series. Field observation and laboratory analysis results show that the formation of clay minerals makes the reservoir properties of carbonate adjacent to the intrusive rocks not good; then, for the carbonate reservoir with acertain distance from the intrusion, it is better in property due to the enhanced fluids dissolution.

Abstract:The reservoir of Xujiahe formation, lying in the central part Yuanba area, belongs to low porosity-low permeability reservoir，and the fractures in this area have important influence on the accumulation and productivity of gas. Based on the core observation, field investigation and well log interpretation, the development characteristics and controlling factors of fractures are studied systematically,according to the regional tectonic evolution. The results shows that there are tectonic fractures, diagenetic fractures and drilling-induced fractures etc. high-angle shear fractures and low-angle shear fractures caused by tectonic are most developed, which are the key types of factures. The main orientation of fractures lies on NW（290°±10°）and NE（75°±10°）. Fractures in this area are poorly filled and are better in petrophysical property. The influencing factors of the fractures development mainly include rock types, rock stratum and the tectonic, etc. The development degree of fractures is different with different lithology; with the increase of layer thickness, the fracture spacing is bigger and the fracture density reduces. The development degree of fractures is sharply decreased. There is a linear relationship between the fracture and he tectonic position. With the distance more and more far away from the faults, the fracture density has a decline trend and the development degree of fractures is also sharply decreased. The comprehensive prediction results of fractures show that the developed zone of fractures is located in both sides of large-scale fault zones, including mainly YL1-YL2（excludingYL2）,YB5-YL5-YB9 in the central part of the area and YB4 -H52 and YL3 in the east part of the area.

Abstract:Calcareous sandstones that are almost dense layers or dry beds are frequently seen in Paleogene reservoir in Bohai oilfield.Geological engineers try all means to avoid this formation. So, finding the reason of forming calcareous sandstone and predicting the distribution of calcareous sandstone is the first work for avoiding inefficient well. This article takes the 3rd member of Shahejie formation in well area 3 of Jinzhou 25-1 oilfield as example, and the result is that there are two conditions for forming calcareous sandstone. One of them is the material condition, the other is the environment condition. The mudstone in the lacustrine facies provides the carbonate flow which is the material condition. The sand which belongs to fluvial facies deposits in the mud, and the sand lens fully contacts with mud. In this situation, the pressure of generating hydrocarbon pulls the flow of carbonate into the sand, and then the flow deposits. The pressure and the facies are the environment condition. The material condition and environment condition are contacted and influenced each other. At the same time, forming calcareous sandstone is affected by facies, contact area and palaeo-geomorphology. At last, considering distribution of sand by seismic facies, this article predicts the area of calcareous sandstone which is located in the western side and beside the depositional center, the eastern side of the smaller depositional center. Geological engineers modified five wells locations to avoid the drilling risk in order not to drill the calcareous sandstone.

Abstract:Based on the content of Ba and ratio method of Sr/Ba in sediment, this paper makes qualitative analysis of sedimentary water body salinity of Carboniferous period in the northeast margin of Junggar basin. On this basis, and combing with the content of clay mineral in fine clastic rocks, we make quantitative calculation of the salinity of ancient water body, and the results show that, in early Carboniferous the ancient sedimentary water body was brackish water to salt water, while in late Carboniferous it was fresh water. Furthermore, the salinity of ancient water body in Carboniferous is far lower than normal salinity of sea water. Comprehensive analysis shows that the northeast margin of Junggar basin was generally located in the margin of continental in Carboniferous. In the early Carboniferous, the sedimentary background of northeast margin was arc-back arc basin and divided by many arcs in plane, as a result, the salinity changed considerably; while in the late Carboniferous, influenced by regional tectonic setting, this area was lifted and became land, and the salinity was decreased in general. Depth analysis of ancient water salinity will have a profound understanding and significance to the Carboniferous tectonic paleogeography and hydrocarbon exploration.

Abstract:The shale reservoir in lower part of member 3 of Shahejie formation (Es3) in Luojia area has significant exploration potential,and the key of exploration is prediction of the distribution character of the total organic carbon. In order to solve the problem of higher cost and less sampling in traditional laboratory measurement, we proposed geophysical techniques to predict the TOC content. Based on the division in shale rock component, using organic carbon rich shale low-density, low-speed geophysical characteristics, we established a single well quantitative estimation formula of TOC to verify the sensitive response relationship of the low impedance for TOC.And, in the use of the well-to-seismic integration method，we predicted the distribution characteristics of TOC on plane. This method obtained a preferable result in TOC prediction of shale in lower Es3 of Luojia area. The maximum relative error of the TOC prediction is 22%, and minimum 0.04%, and the average value is smaller than 9%.

Abstract:Bohai oilfield is a typical conventional heavy oil reservoir, its water flooding recovery efficiency of this type oilfield is quite low, but the potential is great for polymer flooding. Because of the life limit of offshore platform and the risk of development investment,the offshore oilfield polymer flooding should focus on the word of“early”. The feature of injection of early polymer flooding is different from onshore polymer flooding in middle and later period. Reservoir model was established based on related data of typical Bohai heavy oilfield, and the injection timing and pressure feature were studied by numerical simulation techniques. A mathematical model of injection pressure of polymer flooding with influence factors was constructed, the key influence factors were obtained for injection pressure of polymer flooding, including reservoir permeability, oil viscosity, polymer injection timing, etc. Early polymer flooding injection time exists a critical value, and if injection time was greater than the critical value, the injection pressure would increase significantly. The results can provide reference and technical support for the early polymer flooding application of offshore oilfields.

Abstract:The formation is swept incompletely at plane and vertically at later stage of cyclic steam for thick heavy-oil reservoir. There is little potential in reservoir with cyclic steam due to little exploitable reserve of single well. Based on the steam injection mode, the paper has utilized thermal numerical simulation to complete the development system including injection-production system, seepage mechanism and optimization of parameters including horizontal distance between dual horizontal well and vertical well, vertical distance of dual horizontal well and length of horizontal interval. The results reveal that both steam injection by upper horizontal well and vertical well production are critical for the whole system, while lower horizontal wells accommodate the system by flowing back to achieve ideal production. The vertical-horizontal development has become major issue due to its feasibility for further improvement of sweeping volume by steam injection and that of recovery at thick heavy oil reservoir. The producing reserves of reservoir is enhanced due to enhancing the plane sweeping efficiency of the steam with the vertical well and the vertical sweeping efficiency of the steam with the low horizontal well. Optimal development for thick heavy oil reservoir could be obtained with horizontal distance between dual hori? zontal well and vertical well of 50 m, vertical distance of dual horizontal well of 15 m and horizontal section length of 350-400 m.

Abstract:Aiming at the difficulty of pressure maintaining and the low performance caused by steam channeling in heavy oil reservoirs,the physical modeling of profile control and displacement by steam foam flooding was studied in this paper. In order to contrast the oil displacement efficiency and factional flow of different flooding patterns including foam assisted steam flooding and high temperature gas assisted steam flooding, a dual sand-packed tube is designed to accomplish the experiments according to the geological characteristics. The results indicate that the foaming agent or foam, whose oil displacement performance is better than the other flooding patterns,can not only plug the tube with high permeability but also start the tube with low permeability in the model. High temperature gas assisted steam flooding has a slightly better oil displacement effect contrasted with pure steam flooding, and only increases oil recovery by about 1-3 percent. Moreover, the foam can control the flow direction to make the liquid producing capacity of the dual sand-packed tube uniform, this result shows that the foam flooding is suitable for the heterogeneous formation. The contrast in oil displacement performance of different flooding patterns shows that the mixed gas-foam flooding is the best flooding pattern for Fubei 3 block, whose combined oil displacement efficiency reaches 54.8%, which is enhanced by 30.7% contrasted with pure steam flooding.

Abstract:In response to the development difficulties in Xinjiang oilfield, such as poor reservoir properties of low permeability reservoir and poor performances in water flooding, this paper explores the feasibility of using carbon dioxide flooding to enhance the oil recovery and realize the sequestration. The Baqukeshangzu oil reservoir is taken herein for example, and the numerical reservoir simulation is conducted. The prediction model is established based on the fully understanding of typical reservoir development history and its dynamic information by fluid fitting, slim tube test simulation and water-flooding history matching. Besides, the development model,gas-flooding parameters and technologies are optimized respectively. The results show that the minimum miscibility pressure of the reservoir is 18.6 MPa. The carbon dioxide can sweep the area effectively where the conventional water flooding cannot. The sequestration coefficient for the water alternating gas displacement (WAG) is 0.146, which is 12.42% higher than that for water flooding, and 3.33% higher than that for carbon dioxide continuous flooding. The most significant factor that influences WAG efficiency is total gas injection volume. By using control condition to shut down the layers, the sweeping volume of CO2 is expanded, the oil recovery and sequestration capacity are also improved. Its oil recovery is 3.07% higher than that for using control condition to shut down the wells, and its sequestration coefficient is 2.7% improved.

Abstract:In order to explore the new type of biosurfactants which can be applied to the EOR, one kind of lactone sophorolipid biosur?factant was chosen as an oil displacing agent for evaluating the drive oil properties through studying its physical simulation experiment and physical and chemical properties, such as critical micella concentration value (CMC), stability to salinity and temperature, the emulsification value, the effect of core adsorption and physical simulation experiment. The results of physical and chemical properties experiments indicated that the biosurfactant had the good properties in emulsification and reduction of the interfacial tension and surface tension in the complex environment of oil reservoir, such as the high temperature and high salinity reservoir environment. The CMC of the biosurfactant is 100 mg/L, and this kind of biosurfactant could make surface tension of distilled water reduced to 37.1 mN/m and the interfacial tension reduced to 3.07 mN/m. The effective concentration of flooding is 10 mg/L; with the increase of the mass concentration of the surfactant, the oil displacement efficiency increases in double; And, the biosurfactant oil displacement efficiency can reach 7.85% when the concentration of biosurfactant is 10 000 mg/L , which shows good oil displacement performance; By doing experiments, we also found that the quartz sand adsorbed little lactone sophorolipid, which indicates that the lactone sophorolipid biosurfactant is a kind of economic biosurfactant. In Summary, the lactone sophorolipid biosurfactant has great prospects in the field of oil production.

Abstract:At present, the enhanced liquid has become an important measure for improving the development results and achieving stabilized or enhanced oil production. To find out the particularity of water flooding mechanism in high water cut stage for heterogeneous reservoir, the 74-81 unit of Es2 in the block No.2 of Shengtuo oilfield is taken as the experimental simulation unit, and the physical model experiments are used to study the influencing factors and functional mechanism of enhanced liquid result in ultra-high water cut stage, and results showed that the water cut is reduced and then increased in the initial stage of enhanced liquid for single layer, the upward trend is slowed and significantly enhancing the oil recovery, however, depending on increasing the water-flooding pressure to enhance the degree of reserve recovery is not feasible; For enhanced liquid in multi-layer and conventional water-flooding, the stronger inter-layer heterogeneity, the lower degree of reserve recovery of low-permeability layers for the higher permeability layers’intense interference, it is difficult to establish an effective drive differential pressure, on the contrary, the lower the permeability ratio, the higher its oil recovery. The enhanced liquid can significantly enhance oil recovery, and its effect is mainly affected by the reservoir heterogeneity degree, enhanced liquid amplitude and the injection volume; For the enhanced liquid, increasing water flooding differential pressure can enhance waterflooding sweeping efficiency in high permeability layers, and improving the oil producing degree in low permeability.Simultaneously, the balance of displacement velocity and denudation speed is also related to the effect of the enhanced liquid to improve oil recovery.

Abstract:The existence of big channel in high water cut oilfield leads to rapid process of injected water channeling to the production well, aggravation of invalid circulation, which makes the reservoir flooded quickly and reduces the reservoir sweep efficiency and recovery factor. In order to deepen the understanding of big channel, we determine its parameters, the‘invalid water’, named water flowing in big channel, it is calculated by taking full account of the static and dynamic data of oilfield and using seepage theory. Then, according to the high velocity non-Darcy seepage flow formula and Carman-Kozeny formula, the permeability and pore throat radius of the injection-production well can be calculated. On the basis of mentioned above, taking commonly used reverse-five-spot pattern in the oil field for the example, the permeability and pore throat radius among wells are carried out after splitting the water production according to the theory of fuzzy mathematics. The parameters of big channel in an oilfield are calculated by this new method at last, results show that the new method is accurate and reliable. This study provides theory and data support for effectively block the big channel, and has significant application value.

Abstract:In response to the unsuitability of infilling potential evaluation method in an extra-high water cut stage in field, we analyze the oil field development process on the basis of the variation of the well network density conditions and infilling development effect.Based on the research, we establish the rule of well spacing density for infill wells to increase recoverable reserves, and combined with the economic limit of single well recoverable reserves in different prices, we propose a new infill potential evaluation method. The infilling method for extra-high water cut stage oilfield has better adaptability, and is able to guide the infilling potential evaluation for oilfield at extra-high water cut stage.

Abstract:In response to overcome shortcomings of the existing approaches for thief zone classification which concentrates on the absolute index while ignoring relative index, we take Gudong oilfield as the investigation object, employ numerical simulation and reservoir engineering method, and establish type curve for thief zone classification with relative injection rate and injection intensity ratio, on the basis of distinct flow principles, we form different thief zone evolution levels. Moreover, the non-Darcy flow is also taken into account which may occur for severer level, and then the thief zone is classified into four levels: non-thief zone, normal high-permeability layer,high-permeability streak and high-capacity channel. The type curve has conquered the limitations of conventional method, and completely demonstrated the relativity of thief zone, and only injection profile is needed to make the classification, which is very convenient for oilfield application. It has been used to Gudong Ng63+4 development unit, and the classification result is in good accordance with time-dependent reservoir numerical simulation and tracer test, which has substantiated its validity.

Abstract:To conduct better hydraulic fracture design and execution in conglomerate formation, this paper focuses on irregular fracture and pressure fluctuation when the hydraulic fracturing was conducted. The conglomerate was simplified as compound medium which is consisted of three mechanically different parts depending on critical energy release rate, fracture expands or stops. Based on fracture mechanism and coordinate transform, the energy release rate of virtual fracture at the tip of hydraulic fracture is derived, and then the best way for expansion is assigned. The critical fracture pressure is deducted from energy release rate and critical energy release rate.The simulation on morphology characteristics with different size, content, intensity gravels agree accords well with experimental results.Results show that the size and content of gravel, intensity of each part are significant influencing factors for characteristics and pressure fluctuation.

Abstract:The proppant settlement characteristics show the result that, the fluid viscosity has an important effect on proppant settlement which has smaller settlement in the high viscosity than in the low viscosity. In addition, the proppant settlement is not only affected by the fluid viscosity but also subjected to complex fracture networks and composite laying effect of brittle shale. The rapidly fluid back and fracture closure which commonly used in conventional reservoir will lead to proppant back which affects the losses of filled fracture height and the post-fracture production in shale. As a result, it is necessary to keep longer shut-down time to acquire favorable filled fracture height.