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.
