Depositional And Structural Model And Development Of The Es₄ Reservoir In Du66 Block, Western Sag Of The Liaohe Basin

Structures in the basin and structure-controlled reservoir are key factors for the oil and gas exploitation.Combined with multiple techniques,we established isochronic stratigraphic frame,and ascertained four sedimentary facies types,and then their distribution in the Du66 Block was established in this paper.Using the coherence cube technique and ant-technique,we compiled the structures of the study area and recognized two third-order faults and seven fourth-order faults,and defined four structural assemblages.On the basis of the structural feature,effective sandstone distribution and their influence to fine development of oil reservoir,we divided the Es₄reservoir of Du66 Block into four zones,i.e.,namely the north steep zone,the central horst-graben zone,the eastern steep zone and fold zone.We applied the equilibrium profiles and subsidence history analysis to reconstruct tectonic evolution since the Paleogene.The new results of abnormal subsidence analysis show that the post-rift subsidence was primarily driven by the thermal attenuation of the lithosphere.The anomalous subsidence during the post-rift stage could be up to 250m,indicating that the anomalous subsidence was related to the dynamic topography caused by the subduction of the western Pacific plate.Compared with the tectonic evolution of the western depression in the Liaohe Basin,the study area contains both consistence and specialization.The consistence is that the Cenozoic tectonic procedures,both in Du66Block and the western sag depression,are comprised of initial rifting,intense rifting,recapture,the transient stage and depression.Located in the western marginal slope of the western sag depression,the extension and subsidence amplitude of Du66 Block is less than the depression area.Based on the structural analysis,the 3D structure,sedimentary and reservoir models of the Es₄ reservoir in Du66 Block were established by Petrel 3D geological modeling software.The controlling effects of the structures on the sediments and reservoirs were also analyzed.The western boundary fault,which is a syn-sedimentary fault,provides a good channel for the migration of oil and gas.The faults in the block have a blocking effect on the accumulation of oil and gas,which makes the difference of the accumulation of oil and gas in the longitudinal and planar development,and the enrichment of the oil and gas along the western boundary fault.Reservoir magnitude of the difference on fireflooding has reduced by optimizing layer combination and well net development.Based on the study of influence of structure,sedimentary facies,the thickness and the heterogeneity of reservoir to the multilayer fireflooding,the longitudinal extent of the fire line and its degree have improved.Multilayer fireflooding development program for I sandstone group of the Es₄ reservoir in Du66 Block was designed based on the structure model,which yielded good results.The successful implementation of multilayer fireflooding development in Du66 Block directed the development of layered heavy oil reservoir in Jin 91 and Qi 108.Therefore,multilayer fireflooding development has been the key technology for the enhanced oil recovery of deep-layered heavy oil reservoir,and has entered the implementation stage of industrialization for Liaohe oilfield,providing an opportunity for the development of the similar reservoirs.