Reservoir characteristics of the Jiufotang Formation in Nai-1 block of the Naimanqi Depression,Kailu Basin
Ding Feng1,Ding Chaohui2(1.College of Earth Science,Chengdu University of Technology,Chengdu,Sichuan 610059,China;2.Research Institute of Exploration & Development,Liaohe Oilfield Company,PetroChina,Panjin,Liaoning 124010,China)
The PetroChina Liaohe Oilfield Company has expanded its exploration field to the peripheral basins of the Liaohe Oil Field,among which the Kailu Basin is the most prospective one.In this basin,the Upper Jiufotang Fm of the Lower Jurassic in the Nai-1 block in the Naimanqi Depression has good source and reservoir conditions.However,no systematic research has ever been carried out on the sedimentary facies and reservoir features of this study area.Therefore,based on the previous study results and in combination with core,drilling and logging data,we performed a comprehensive study of the Jiufotang Fm reservoirs.The following conclusions are drawn.(1) The Upper Jiufotang Fm belongs to a fan delta sedimentary system which can be divided into fan delta frontal subfacies and several microfacies like interdistributary bay,lateral border of underwater distributary channel,mouth bar and underwater distributary channel.(2) Reservoir pore types are dominated by dissolution pores and relic intergranular pores and certain micropores.They are reservoirs of moderate-low porosity and low-ultra-low permeability.(3) Sedimentary microfacies,lithology and diagenesis control reservoir development.Underwater distributary channel is the most favorable reservoir facies,followed by mouth bars.(4) Feldspar and quartz overgrowth and authigenic mineral infilling have an adverse effect on reservoir development.(5) Although secondary dissolution is constructive to reservoir development,but its contribution is limited.