| The Ng35 reservoir of Lin93 Block in Linpan Oilfield is located in the southwestern of Jiyang Depression in the Bohai Bay Basin,and the down section of the Linyi fault and the shallow layer of the Dalujia rolling anticline.In the process of exploration,the production degree of reservoir is low and the development contradiction is prominent.Many scholars at home and abroad have conducted a lot of research on this area,and the following problems still exist:the division of single sandbody in the stratum is not precise enough to meet the needs of current exploration and development;the conclusion of sedimentary microfacies type and sedimentary evolution model has not been unified;insufficient research on reservoir heterogeneity,lack of comprehensive evaluation and classification work;the distribution of residual oil is not clear,the overall recovery rate is low.In order to improve the development effect in this area,it is necessary to carry out more detailed basic geological research to provide geological foundation for reservoir numerical simulation and later development in study area.Guided by high-resolution sequence stratigraphy,reservoir geology,sedimentology and other theories,this paper comprehensively utilizes well logging,Mud logging,core,seismic,analysis and laboratory data to study stratigraphic division,sedimentary facies and reservoir comprehensive evaluation and classification of the reservoir of Ng35 in Lin93 Block.The following main achievements and understandings have been obtained:Under the control of the marker bed,the marker interfaces of oil layers,sand group and small layers are identified and the single sandbody is subdivided by core-thickness identification method.From top to bottom,three single sand layers are divided into Ng35-1,Ng35-2 and Ng35-3.Finally,the fine stratigraphic framework of the study area is established.According to the color of mudstone and the distribution of sandstone composition,it is considered that the sedimentary environment is oxidized and the provenance comes from the Northwest direction.According to the analysis results of petrological characteristics,grain size,sedimentary structure characteristics and lithofacies characteristics of samping wells,it is concluded that a set of braided river sedimentary reservoirs are developed in the target formation,which can identify sedimentary microfacies such as channel filling,mid-channel bar microfacies and flood plain,depict the spatial distribution of sandbodies and sedimentary microfacies,and establish sedimentary evolution model.The scale of the river is declining from bottom to top.Based on the study of sedimentary microfacies,the macro-physical properties,micro-pore throat structure and heterogeneity of the reservoir are studied in detail by means of thin section observation,scanning electron microscopy and laboratory analysis.It is considered that the reservoir have the characteristics of medium-pore and medium-high permeability,sandstone intergranular pore is well developed and pore throat structure is good;the single sand layers of the target layer belong to serious heterogeneous reservoirs,the interlayer heterogeneity of Ng35-2 and Ng35-3 is strong,the reservoir plane changes rapidly,the thickness and physical properties are controlled by sedimentary facies zones,and the overall in the regin plane heterogeneity is serious.By synthesizing the sedimentary facies,reservoir characteristics and comprehensive evaluation results of the study area,seven parameters representing macro-physical,sedimentary and micro-pore throat structure characteristics of the reservoir are selected.Referring to the classification criteria for evaluating porosity and permeability of oil-bearing clastic rocks,the reservoir classification criteria are finally established.The reservoirs in the study area are divided into three categories,of which type I reservoir has the best physical properties and well-developed pore throat structure,mainly developed mid-channel bar microfacies.Which is an favorable target in the study area. |
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