The determination of the growth and morphology of acidizing wormholes is the research foundation of carbonate rock stimulation.The acidizing technology of carbonate reservoir mainly includes matrix acidifi-cation and acid fracturing.The two kinds of processes have different regulation directions for acidizing worm-holes.The key to matrix acidification is to promote the wormhole growth,and the production of wormholes needs to be inhibited during acid fracturing.Based on the geological characteristics of a low-permeability carbonate gas reservoir in eastern Sichuan,a two-scale acidizing wormhole growth model was established.The effects of geological factors such as porosity and permeability distribution,as well as engineering factors such as acid concentration,acid injection rate,and acid viscosity on the growth morphology of wormholes were analyzed from the perspectives of radial and axial models.The results indicate that permeability and porosity have an obvious effect on the growth of wormholes.The effects of engineering factors on wormhole growth were as follows:injection rate＞acid concentration＞acid viscosity.
Chemical flooding in Daqing Oilfield has gradually shifted to class-Ⅱ reservoirs with stronger heterogeneity,poorer connectivity,lower physical properties,more type of injection in thin layers and pro-duction in thick layers,and more type of injection in thick layers and production in thin layers.As a result,the development effect of polymer flooding is not ideal,and the difficulty of tapping potential of remaining oil is increased.In view of the problems of fuzzy identification method of injection-production connectivity type and unclear corresponding polymer flooding development strategies,the method of reservoir numerical simulation combined with dynamic analysis is adopted to study the identification method of injection-pro-duction connectivity type and define the polymer flooding development strategies.The results show that when the connectivity thickness is greatly different,that is,when the thickness ratio of thin-layer to thick-layer is less than 0.3,the effect of polymer flooding will be affected.The injection-production connectivity type of polymer flooding reservoir is innovatively defined by using the thickness ratio method,which overcomes the problem of inaccurate identification criteria in the past.For the type of injection in thin layers and pro-duction in thick layers,the injection well should adopt low concentration injection to properly increase the injection rate during polymer flooding,and the oil layer should be reconstructed with fracturing measures at the initial stage of polymer flooding,and the polymer flooding effect is good.For the type of injection in thick layers and production in thin layers,high concentration injection should be adopted while reducing the injection rate.It's not easy to conduct fracturing at the early stage of water cut recovery in oil well end frac-turing,which can achieve better polymer flooding effect.The precise identification of the connectivity types of injection-production wells and the development strategies can provide theoretical basis and technical support for the improvement of the quality and efficiency of polymer flooding in class-Ⅱ reservoirs.
In recent years,breakthroughs have been made in oil and gas exploration in the Mahu Sag,but there is less research on the control of heterogeneous diagenesis in sandy gravel reservoirs.The first member of the Upper Permian Urho Formation in the Mahu1 well block is a typical strongly heterogeneous sandstone reservoir with low compositional and structural maturity.Based on data such as cast thin sections,reservoir physical properties,and scanning electron microscopy,the damage and construction effects of diagenesis on reservoir physical properties were analyzed,and the main reason for the high content of secondary dissolved pores is clarified,which is the dissolution of tuff debris and feldspar in the study area.Zeolites have a strong cementation and destruction effect on reservoirs in the early stage of diagenesis,but after entering the middle diagenetic stage A,a large number of zeolite dissolution pores are formed,becoming an important component of secondary dissolution pores.Meanwhile,there is a large amount of iron calcite and filamen-tous illite in the reservoir of the first member of the Urho Formation,indicating that the first member of the Urhe Formation in the Mahu1 well block is currently in the middle diagenetic stage B.
With superior reservoir forming conditions,large and medium-sized oil and gas fields of different trap types in Pingbei slope belt are distributed in groups and belts,which is the main exploration area of Xi-hu Sag in recent years.However,with the improvement of geological understanding and exploration degree,the exploration of traditional structural and lithologic reservoirs has entered the middle and late stage and it's urgent to find new exploration areas.Based on structural patterns of alternating depression and uplifts with high west and low east of Pingbei slope in the plane view,combined with the sedimentary filling background of clastic rocks in symbiosis with volcanic rocks in this area,focusing on the evaluation of subtle traps,through comprehensive analysis of structure,sedimentation and seismic,it is believed that the Pingbei slope belt also develops three types of subtle traps,including stratigraphic-lithologic traps,buried hill traps,and volcanic traps.In view of the geophysical response characteristics of different subtle traps,different geo-physical identification techniques have been established.Spectral decomposition technique with different fre-quencies can identify specific stratigraphic pinch points,thereby effectively identifying stratigraphic-lithol-ogical traps.Amplitude/frequency attribute volume can identify weathering leaching zones.Ant body crack identification technology can identify the location of crack development,thus achieving the identification of paleo-buried hill traps.The above techniques have achieved good evaluation in application,and can pro-vide a good technical guidance for subtle traps exploration in Pingbei slope belt.
After 20 rounds of steam stimulation in Jinglou Oilfield,80％of the geological reserves are still trapped underground,making it difficult to recover by using the current well pattern.In response to the ex-isting problems,the spatial distribution of"beaded-shaped"and single"beaded"remaining oil in shallow layer heavy oil reservoirs are described by means of coring analysis and numerical simulation of inspection wells.Therefore,infilling horizontal wells around the"beaded-shaped"remaining oil is deployed.Collab-orating with the development strategies of the original well pattern,a new technical idea for extending the life cycle of similar reservoirs is provided.
A-grade oil well cement is mainly used for surface cementing in Andes block of Ecuador,and the abnormal increase of displacement pressure occurred many times during cementing process.Aiming at the problem that low flow speed and low shear rate may affect its hydration reaction speed during injection and displacement,the influence of low shear rate caused by low return velocity cementing is studied.The results show that under the condition of low shear rate,the hydration reaction speed and process of cement slurry are accelerated,and the thickening time is greatly shortened,which makes it easy for early thickening of cement slurry,while the suspension stability and compressive strength of cement stone are not affected.According to the influence of low shear rate on the performance of cement slurry,the cement slurry design is optimized,and the abnormal of early thickening displacement pressure of surface cementing slurry is solved.
Located in Liyuan area near the boundary fault in southern steep slope zone of Biyang Sag,affect-ed by the boundary fault activities,Bi 358 block is a nose-shaped structure with fast accumulation of con-glomerate deposits in the third member of the core.The reservoir is highly heterogeneous and the distribution of sweet spot reservoirs is unclear.In order to improve the rolling exploration and development effect of sandstone and gravel rock mass,starting from the division of sandstone and gravel fan stages,through the reservoir seismic response characteristics analysis,the texture characteristics of seismic data are processed based on the sedimentary mechanism of sandstone and gravel,and favorable facies zones are characterized using grayscale energy attributes.The results indicate that there are multiple nearly north-south trending waterways developed in fan subfacies,the forward distance is controlled by the length of the waterways and the sweet spot reservoirs are mainly developed in the fan subfacies.
In response to the problem of high water output in some gas wells and the inability to sustain pro-duction relying on the formation energy itself,several typical high yield water gas wells were selected to con-duct the electric submersible pump drainage and production process tests.The results indicate that through downhole gas-liquid separation,frequency conversion anti-gas,remote intelligent monitoring,and sand control design,the pump adaptability in shale gas wells is improved.Taking JD-2 well as an example,the pump drainage and production technology eliminates wellbore fluid accumulation,ensures continuous and sta-ble production of gas wells,and meets the drainage requirements of a vertical depth of 3 500 meters or more.
The mixed deposition in Da'anzhai section of Zhongjiang gas field in western Sichuan depression is relatively developed.Through observations such as outcrops,cores,thin sections,and scanning electron microscopy,it is shown that the Da'anzhai section develops mixed rocks such as crust limestone,(inclu-ding)muddy crust limestone,(including)sandy crust limestone,crust mudstone,and limestone feldspar lithic sandstone.There are two types of mixed deposition:intermittent mixing and in-situ mixing.Mixed rock reservoirs are generally relatively dense under the influence of diagenesis,and a certain degree of mud mixing can improve the physical properties of the reservoir.Excessive mixing of mud will inhibit reservoir permeability,and the muddy crust limestone reservoir is a dessert reservoir.Huilong area is a favorable area for exploration and development in the Da'anzhai section.
Gas logging data contains a large amount of stratigraphic information,which is valued for its ad-vantages such as real-time,sensitive,quick-response,and low human factors.It is mainly used for oil and gas display recognition and evaluation,and the expansion of its application can fully realize its value.The article introduces the feasibility,application methods,and application examples of using gas logging da-ta to assist in establishing geological profiles,comparing and determining the actual drilling strata,geolog-ical guidance,pre-pressure evaluation of tight sandstone horizontal wells,and assisting in determining the location of breakpoints.
Multiple sets of sand bodies are developed in Yan9 reservoir in Xincheng Block of Jingbian Oil-field,and the degree of water drive control is low.By using methods such as logging data,core analysis,and mercury intrusion experiments,the heterogeneity characteristics were studied,and the heterogeneity of the Yan9 reservoir was qualitatively evaluated and its genesis was briefly analyzed.The results show that the pattern and scale of channel deposition in the early Middle Jurassic determined the distribution of reservoir in plane.The Yan9 reservoir in Xincheng block of Jingbian oilfield is banded in the direction of northwest to southeast,and the distribution of porosity and permeability are closely related to the distribution and devel-opment status of sand bodies.Based on the calculation of heterogeneity parameters such as stratification co-efficient,sandstone density and variation coefficient,extensive and stable interlayer increases the interlayer heterogeneity and has an important effect on hydrocarbon migration and accumulation.Intercalations are generally developed but have poor continuity in each small layer of the reservoir,permeability is dominated by reverse-positive rhythm and position-positive complex rhythm,and the Yan922 small layer has strong heterogeneity.The results can deepen the understanding of reservoir characteristics of Yan9 formation and provides guidance for fine waterflood development in the block.
To evaluate the well pattern adaptability for marine sandstone reservoirs in the eastern South Chi-na Sea,a comprehensive study is carried out from four dimensions:infilling potential,well pattern interfer-ence,reserve utilization and development status.Based on the ultimate oil displacement efficiency correc-tion of the Cherkachov formula,the well infill boundary is clearly adjusted in combination with economic factors.The infilling potential is considered from both technical and economic perspectives.By analyzing the reservoir and single well water drive characteristic curves,the well pattern control reserve interference parameters is established for evaluating the degree of well pattern interference.By material balance method,the percentage difference in water driven reserves is established for determining the degree of reservoir re-serve utilization.The classification and evaluation criteria for production effectiveness is established through three indicators:average oil recovery rate,maximum oil recovery rate and reservoir recovery degree.By an-alyzing four types of evaluation indicators,when there are more than two unfavorable indicators,the defini-tion of reservoir well pattern is unsuitable,and it's applicable when there are more than two indicators.Through quantitative evaluation and analysis on well pattern development of typical oil reservoirs,this meth-od is able to quickly and efficiently evaluate the well pattern of oil reservoir development,and also provide reference for the adaptability analysis of similar oil reservoirs.
The western slope of Xihu sag is one of the most important exploration areas in the East China Sea Basin,but the Tiantai slope in the south is located in the intersection area of Haijiao uplift and Yushan low uplift.Unclear provenance system restricts the study of sedimentary reservoirs.Based on the methods of zir-con morphology,detrital zircon U-Pb dating and seismic progradation reflection,the difference of the Pa-leogene provenance supply characteristics between Haijiao uplift and Yushan low uplift was made clear,and then the relationship between material source and strength of different layers in the provenance intersection area of Tiantai slope was determined.The results show that during the Pinghu Formation,the Tiantai slope is located in the arc fault transportation area,the source is jointly supplied by Yushan low uplift and Haijiao uplift,and the sediments are distributed along the fault transition zone to the lower position.During the Huagang Formation,the source supply of Yushan low uplift weakened,and the source supply of Haijiao up-lift continued to strengthen.
Multiple sets of tight sandstone gas reservoirs are formed vertically in the upper Paleozoic in Linx-ing area,with various sensitivity damage rates and differences in sensitivity among different strata.Com-bined with X-ray diffraction,thin section analysis,scanning electron microscope,nuclear magnetic reso-nance and sensitivity test,the reservoir sensitivity and controlling factors were analyzed.The results showed that the water sensitivity and salt sensitivity in the study area are generally strong affected by rock mineral composition and reservoir physical properties.In vertical direction,the acid sensitivity and alkali sensitivity of different reservoirs show an opposite trend.Reservoir sensitivity is affected by clay mineral type,content and pore structure in microscopic view.The water sensitivity damage is mainly affected by illite-montmoril-lonite mixed layer.The acid sensitivity and alkali sensitivity damage rates are correlated with the content of chlorite and kaolinite.With the deterioration of pore structure,bridging authigenic minerals are easy to transport and block the small pore throat reservoir and cause damage.Reservoir sensitivity is controlled by sedimentary microfacies and diagenesis in macroscopic view.Good sedimentary microfacies have strong hy-drodynamic force,in which the sandstone has high clastic content,low clay mineral content,good pore con-nectivity,and weak velocity sensitivity and water sensitivity.According to diagenesis,pore type,porosity and permeability,the diagenetic facies of the reservoir can be divided into four types.Among them,the sensitivity of the siliceous cemented intergranular(Type Ⅰ)diagenetic facies and feldspar dissolution pores(Type Ⅱ)diagenetic facies is relatively weak,and belongs to high-quality reservoir types.In vertical di-rection,the sensitivity difference of different formations and different diagenetic facies can provide reference basis for optimizing reservoir protection measures.
The carbonate gas reservoir of the fourth member of Dengying Formation in the platform margin of Moxi Block,Sichuan Basin is a strong heterogeneous gas reservoir,which has diverse reservoirs,complex permeability and great difference in production dynamics.At present,based on reservoir identification from core,imaging logging,conventional logging and etc.,the reservoir classification is carried out.In order to improve the identification accuracy,and provide a reference for development countermeasures of different types,through analysis of well test data and the dynamic characteristics,the reservoir is divided by classifi-cation.In addition,according to the analysis and comparison of well test interpretation and production per-formance characteristics,the reservoir identification accuracy is further improved from the production dy-namic characteristics.Research results suggest that the reservoir types can be divided into four categories based on the dual logarithmic curve morphology of well testing:fractured-vuggy,vuggy-fractured type,double vuggy and fractured types.After acid fracturing transformation,the seepage conditions of reservoirs near the gas wells are better than those of the same type in the far well area.Fractured-vuggy and vuggy-fractured gas wells are superior to fractured ones in terms of stable production capacity,open flow rate,and dynamic reserves.The initial open flow rate in porous and fractured reservoirs varies greatly,while the over-all decline rate in fractured reservoirs is relatively high.The established classification method can improve the accuracy,and then classify and manage gas wells to achieve efficient development.
Multi-stage fracturing of horizontal wells is the main production method for unconventional reser-voirs.It's important to determine the scope of artificial fracturing transformation for optimizing the orienta-tion,fracturing section division plan and well spacing selection before drilling.The material point method was used to simulate the interaction between artificial fractures and natural fractures.The scope of artificial fracturing was determined,which was consistent with the distribution range of micro-seismic events,and the horizontal orientation and average length of the developed and undeveloped fracture zones were opti-mized.The results show that the application of material point method can effectively predict the artificial re-construction range of hydraulic fracturing,optimize the horizontal orientation and completion plan,and pro-mote the efficient development of unconventional reservoirs.
At present,the determination of the time for shale gas flowback and oil nozzle system mainly re-lies on experience,lacking scientific and systematic theoretical basis.In order to achieve the beneficial de-velopment of shale gas,9 developed horizontal wells on the H36 platform of the Wufeng-Longmaxi Forma-tion shale gas reservoir in the Changning area were selected for analysis,and 3 wells were evaluated for post pressure flowback optimization models.The results indicate that there are differences between the actual and theoretical flowback results in terms of shut-in time and nozzle system,and there is a potential improve-ment space of 5％～10％for the final recoverable reserves.It is recommended to use a flowback optimiza-tion model to determine a reasonable shut-in time and nozzle system,so as to improve the final recoverable reserves in the single well stage and the overall development effect of the platform well.
An ultra deep water horizontal well for drilling multiple biological reef gas reservoirs was newly deployed in Yuanba block.Faced with difficulties such as slow drilling speed,easy leakage in the Changx-ing Formation,and long drilling cycles,as well as difficulties in controlling the trajectory of the long hori-zontal section of the small wellbore,and difficulty in placing the perforated liner in place,it is difficult to drill in continental Zhenzhuchong and the Xujiahe Formations.By optimizing the design of wellbore struc-ture,selecting directional drilling tools,and optimizing trajectory control methods,researching and selecting drill bits that match the characteristics of the formation and meet the requirements of composite drilling,matching high-performance drilling fluids,and improving the technology of pipe string insertion in ultra deep wells,key technologies for drilling ultra deep and long horizontal sections in Yuanba have been formed,which completed the construction of the first ultra deep horizontal well in Yuanba,with a length of 1 464 meters and a depth of 8 425 meters.The drilling cycle is 237.38 days.Compared with the shortest drilling cycle in Yuanba 102-3 H in the early stage,the well depth increases by 697 meters,the drilling cycle is shortened by 15.87％,and the average mechanical drilling speed is increased by 23.88％.
In view of the cementing problems in high water cut blocks of Dagang Oilfield,the influence of the dispersion resistant BCY-100L on anti dispersion,anti-channeling and comprehensive performance of cement slurry was evaluated by referring to the experience of underwater non-dispersed cement slurry in construction industry.After adding BCY-100L,the loss of cement slurry is not more than 1％,the pH val-ue is not more than 9,the water-to-ground strength ratio is not less than 0.75 and cement slurry has good resistance to water invasion.The water non-dispersed cement slurry had short static gel strength transition time,no gas channeling,greatly improved anti-channeling performance,and good performance of reducing water loss.Besides,it has little effect on the thickening time and compressive strength of cement slurry,and the comprehensive performance of cement slurry is good,which can meet the requirements of site con-struction.This cement slurry has been successfully applied 7 times in Dagang Oilfield,which helps to im-prove the sealing quality of oil,gas,and water layers.
During the ultra-high water cut period of water drive oilfields,with the deepening of water drive development,the water saturation increases,and the water phase permeability in the permeability curve rap-idly increases.In later oilfield development stage,under high water multiple,the water phase permeability will sharply increase,showing a phenomenon of Kro/Krw and Sw relationship curve rapidly deviating from the straight line,resulting in the invalid water circulation zones.In order to solve this problem,it is necessary to conduct in-depth research on the identification methods of invalid water circulation zones.Therefore,based on the analysis of the actual core and development dynamic data of Bohai B oilfield,and oil wells with a water content higher than 90％were selected.The variation of water content derivative in a single well and the water drive characteristic curve were analyzed.Oil wells with peak water content derivative and deviation from the straight line and upward trend of the water drive characteristic curve were identified as having an invalid water circulation zone,and the identification method was clarified.By using this method,high water cut oil wells in Bohai B Oilfield were screened and corresponding control measures were implemented,a-chieving good oil increase results.
