Reservoir Architecture Anatomy Of Typical Sand Body

As the research hotspots in sedimentary studies,braided river deposits and meandering river deposits are the most important reservoir types among the fluvial facies.In recent years,scholars have conducted researches on the meandering river sedimentary reservoirs and their internal structures,and have proposed sedimentary models which are generally accepted.However,researches on the braided river sedimentary reservoirs and reservoir architecture are still underway and there are no more mature understanding and research results.For the braided river sedimentary reservoirs,the internal sedimentary units may show different physical properties under different sedimentary environments.Based on the traditional braided river sedimentary model,the analysis of the architecture of the reservoirs may not fully explain the internal structural characteristics of the sandstone,and thus it may not be able to properly understand the different types of braided river reservoirs.It has become an urgent requirement to make a supplement and re-recognition to the traditional model of braided river deposit so that it can make more detailed description of the reservoir architecture.The main layers of the Guantao Formation in P oilfield belong to braided river sedimentary sand bodies.In the process of research,it is found that the sand body characteristics are different from the traditional braided river sedimentary sand bodies,and it is difficult to carry out the reservoir architecture analysis according to the braided river sedimentary model proposed by the scholars.Thus,how to reconstruct the architecture of reservoirs has become the key to realize the remaining oil and improve the recovery rate of reservoirs.In this paper,the main layers of the Guantao Formation in P Oilfield were taken as the research object.Based on the geological background of the study area and the understanding of the sedimentary characteristics of the main layer sand bodies,the exploration practice of main stratum of the P oilfield,outcrop investigation and modern sedimentation survey were combined.According above,the traditional braided river sedimentary structure model was supplemented,and the corresponding internal anatomy of the reservoir structure was proposed.And then the main layer of the Guantao Formation was finely dissected and the reservoir architecture of braided river reservoirs suitable for the study area was established.In accordance with the above ideas,this paper mainly studied from the following aspects:First of all,the geological background of P oilfield was investigated,and it was determined that the main layers of the Guantao Formation were the sedimentary environment of the braided river.Secondly,based the survey of the sedimentary structure of the braided river,the outcrop of the braided river was investigated.The Wuguantun section was selected as the outcrop section which is located in Yungang Town,Datong City,Shanxi Province.And the outcrop profile and the main strata of the study area were compared from the aspects of climatic characteristics,reservoir characteristics,and structural element characteristics.It is found that the characteristics of the sand bodies are similar to those of the sand bodies developed in the study area.At the same time,it is found that the sedimentary structure of sand bodies is not the same as that of the traditional braided rivers.In addition to the development of sand bars,channels,and abandoned river channels,some other units such as chutes and abandoned pits have also been developed.On the other hand,a modern sedimentary survey of braided rivers was conducted.The braided river section of Shengli River was selected as the investigation,which is located in Luotian County,Macheng County,Hubei Province.The scale and water velocity of typical sand bars were measured,and the formation of sand bars was analyzed in combination with the measurement data.It was confirmed that the sedimentary structural units included sand bars,channels,chutes,abandoned pits in the section of the river.Using reservoir analytic hierarchy process,the sand bodies are dissected as the hierarchy of “brained channel belts-complex sand bars-single sand bar-channel-inter elements”.In the study,the thick oil layer in the dense well network area divided by the study area was used as an example.First,the skeleton profile was established and the standard layer was determined using the mudstone at the top and bottom of the thick oil layer.Second,the comparative profile was made through bottom leveling.Third,based on the characteristics of logging curves,the complex sand bars were identified,and the single sand bar can be identified using the characteristics of the return curve and the characteristics of the cycle within the complex sand bars,so that the area of sand bars could be tracked and identified in the three-dimensional space.Based on the single cross-section contrast and the three-dimensional closed section,combining with the contact relationship between sand bars,the space evolution of sand bars was analyzed and the formation of sand bars was reproduced.Based on modern sedimentary surveys and outcrop investigations,the formation process of sand bar was taken into account and the architecture of the braided river sand bodies in the study area were determined,which was not the same as the traditional braided river sedimentary model.And thus on basis of the traditional one,it has been supplemented to provide new ideas and methods for the remaining oil in the later research and development,and ultimately it could improve the oil recovery.