Geological Characteristics Of Reservoirs In Mortuk Oilfield

The Mortuk Oilfield is located in the Inbek-Zalkames uplift belt in the eastern part of the Pre-Caspian Basin,influenced by the salt dome structure,the distribution characteristics of fault system and sand body in the study area are not well understood,which leads to low output.In this paper,seismic,geological,logging and core data are used comprehensively to study geological characteristicsUsing the core and logging data to determine the contrast mark of the sand layer group,and looking for the auxiliary mark layer,controlling the small layers,taking the seismic data as the constraint,and comparing the well logging curve as the main means to compare the wells and establish the isochronous stratigraphic framework.On this basis,through the combination of well and seismic,the horizon calibration of single well and continuous well is used to determine the interpretation scheme of the target horizon,using the method of seismic reflection wave phase axis misalignment,coherence slicing and continuous well comparison identify the faults;using "horizon control method" established velocity field,complete the T-D conversion,and analyze the structural features of the oilfield.The sedimentary facies study is carried out by combining the core description with the coring rock combination characteristics,and the sedimentary facies research of non-coring wells is carried out by classifying the rock and electrical response characteristics.In the case of implementation of the structural form,the sensitive parameters of the reservoir are analyzed,and the sedimentary is constrained.The seismic waveform indicating inversion method is used to predict the reservoir sand body of the main target intervalThe results show that the Jurassic and Cretaceous strata cover the salt dome uplift and form a short-axis anticlinal structure around the salt dome,which is steep in the west and gentle in the east,the faults is developed at the top of the anticline,there are relatively few faults on the two wings,and four large positive faults develop at the bottom of the two wings,forming two mantles distributed around the salt domes;both the Cretaceous and the Jurassic are sub-facies of the delta front,and further define the microfacies such as the underwater branch channel,the estuary dam,the far sand dam and the tributary bay,the Cretaceous reservoir is mainly composed of underwater branches and dams,sand is thin and continuity is good,and it has the characteristics of lap joint,the Jurassic reservoir is mainly composed of underwater branch channel sand bodies,the thickness is large,the sand bodies are stacked and deposited,and the continuity is poor;the reservoir is dominated by medium-fine sandstone and fine sandstone,the Cretaceous reservoir has the characteristics of high porosity and permeability,the Jurassic reservoir has the characteristics of medium-high porosity and high permeability;the Cretaceous has the characteristics of "mud-packed sand",mainly composed of mudstone,the main oil layer is the distributary channel and the estuarine dam composite sand body at the bottom of the K1br group,it is stably deposited in the whole area,and the Jurassic system has"sand-packed mud",the characteristics are mainly sandstone,the main oil layer is K3-1 and K3-2 layer of underwater channel sand body,it is developed in the whole area,and the sand body in the north is slightly better than the south.