Research On The Gas Reservoir Of Jialingjiang Formation In The Southern Puguang Gas Field

Puguang Gas Field belongs to Shuangshimiao Puguang Tectonic Belt in Northeast of Sichuan Basin.After exploration and development for more than ten years,the main aeration zone of this rock composite large gas reservoir,that is,Feixianguan Formation of the lower Triassic series and Changxing Formation of the upper Permian series,needs to broaden new areas for exploration and development due to its limited reserves.With the advance of awareness and technology,the thin-bed reservoirs have gradually become one target to increase the reserves.In view of the geologic features and the development status quo of the gas reservoirs in Jialingjiang Formation in the South Puguang Gas Field,guided by scientific theories such as oil-gas field development geology,fossil oil geology,carbonate sedimentology,reservoir geology,etc.,integrating various exploration data and supported by computer technology,this research applies technologies and methods like earthquakes,well logging,reservoir prediction,detailed reservoir description and so on,describes the tectonic features,fault features,fissure features,reservoir features,sedimentary face features and the diagenesis in Section ? of Jialingjiang Formation and reveals the remaining amount and distribution of the reservoir,thus laying a good foundation for the research to track the tectonic of thin-bed reservoirs,to increase production of the gas fields and to locate and explore the reserves of the remaining gas.Using data of 3D seismic,well drilling and well logging,etc.and based on the comparison of framework sections,the paper divides Jialingjiang Formation into 5 subsections,makes detailed tectonic research about Jia-? Subsection in the area,compiles high-precise and large-scale tectonic maps for each subsection and reveals the small-range and micro-structure distribution features and the development and distribution rules of the small faults.Based on the previous researches and analyses about the sedimentary background,the paper makes researches on the reservoir's sedimentary parfacies and microfacies by outcrop description,drill core observation and sheet analysis.The paper deems that the sedimentation of Jialingjiang Formation experienced two cycles of sea level rise and fall and mainly developed into 3 facies including open platform,restricted platform and evaporation platform.The 3 facies are further divided into six parfacies including beach interact sea,grain banks,restricted lagoons,restricted tidal-flat,etc.as well as several corresponding microfacies.Among them the grain banks are comparatively good development area of reservoirs.The paper makes researches and analyses about the reservoir diagenesis and its features via many methods such as drill core observation,sheet analysis,granularity,general physical parameter analysis,etc..The research suggests that the main diagenesis in the area includes dolomitization,dissolution,mud crystallization,compaction,pressure solution,cementation,recrystallization,filling action and fracturing.Among them cementation,compaction and filling are detrimental to the formation of reservoirs,while dolomitization,pressure solution and tectonic fracturing are important constructive diagenesis types.Bio-diagenesis and recrystallization have little effect on the reservoir properties.The paper also makes researches on the physical parameters of the reservoir and pints out that it mainly is a low-porosity and low-permeability reservoir.According to the evaluation standard of reservoir classification,the target reservoir in the area under research mainly develops into Type ? and partly into Type ? and Type ?.On the basis of the geologic features of the thin-bed reservoir in Section ? of Jialingjiang Formation,the main target reservoir in the area under research,the paper makes revisions and standardization about the drilling well data,systematically analyzes the physical parameters about its rock,constructs a reservoir model and carries out a forward modeling using frequency properties.According to the results of the forward modeling,there is no obvious response on the forward modeling section when the reservoir is less than 14 meters thick.When the thickness of the reservoir is bigger than 14 meters,there appears polarity reverse or enhanced amplitude on the bottom limit of the gypsum bed of the reservoir.With the increase of the reservoir thickness,the amplitude on the bottom limit of the gypsum bed gradually becomes bigger.On the base of the forward modeling,the quantitative forecast of the reservoir is done by several classic seismic inversions including band-limit inversion,sparse spike inversion,color inversion,NN inversion and model-based well logging constrained seismic inversion.The results suggest that the model-based well logging constrained seismic inversion has higher resolution and better regularity in lateral variation,thus a good match with the well.Based on these inversions,the thickness distribution of the reservoir of Jialingjiang Section ? has been mapped and the reserves are evaluated according to the map.The research indicates that to think broadly and combine various pertinent comprehensive prediction methods is an important approach for increasing prediction precision and result reliability.The research methods of this paper are of very important guiding significance for the development of the Jialingjiang Formation in the Southern Puguang Gas Field.They are also a good reference for the development of gas reservoirs of the same type.