Study On Sedimentary Facies Of The4^th Member Of Shahejie Formation In Bamianhe Oil Field

This paper takes sedimentology, petrology, sequence stratigraphy, geophysical logging and other theory as a guide, and makes use of core, logging and previous research results, based on the sign recognition of the study area and background research, under the control of the framework of isochronous stratigraphic correlation, by the research thinking from the pointâ†'lineâ†'surfaceâ†'body, following the technical route from the sedimentary facies identification and division, to a single well and sedimentary facies analysis of the associated wells and to planar distribution of the facies. The micro-facies of the fourth member of Shahejie formation in Shaziling of Bamianhe oilfield was studied, and also the types of sedimentary facies and their spatial distribution law were analysed. It reveals the planar distribution of sedimentary facies and their vertical evolution law from a macro perspective and makes the analysis and prediction of favorable sand.Shaziling area is located on the northeast of Bamianhe oilfield, which is connected to the main body of Dongying depression on the west, and on the east to Qingdong depression, on the north to Qingnan subsag and Qingtuozi salient and on the south to Weibei salient, from south to north it is8km wide and from east to west it is about12km long, having the exploration area of about100Km2. Shaziling area is part of the south slope of the entire Dongying depression and which is also considered to be the south slope of Qingnan subsag. The study area can be divided into three blocks and the main oil bearing formation is the fourth member of Shahejie formation.Based on the decription of the macro observation and microscopic characteristics of coring wells, from the aspects of rock characteristics, the particle size distribution characteristics, sedimentary and tectonic features, paleontology, trace fossils and logging features, the facies marker was summarized, in the study area lacustrine and delta were identified and there are two kinds of subfacies and thirteen kinds of microfacies. Through fine stratigraphic correlation, the stratigraphic correlation framework was established, thereby establishing ten associated wells and analysing eight single wells. The microfacies on the correlation section were analysed and compared, the vertical and horizontal evolution of sedimentary facies were also analysed, building the sedimentary framework of the study area. According to the mudstone color change characteristics and the location of lake, the depocenter of the study area and its migration law were analysed and the sedimentary model was establised, with the consideration of the tectonic setting, stratigraphy and sand body distribution law, the sedimentary source of the study area was recognized.It is believed that during the middle-late period of the fourth member of Shahejie deposition, Shaziling area shared the sedimentary source from Guangrao and Weibei, with the change of sea level and supply of source, the delta and lacustrine facies were developed in the medium-term, and it was mainly lacustrine deposition in late period; in the plane, the lacustrine facies developed in most regions of the study area, while the delta facies developed mainly in the southeastern part of the study area; the delta front deposition was developed well, in the proximal part it is mainly subaqueous distributary channel and in the distal part it is mainly sheet sand and distal bar; the shallow lake sub facies is dominant in lacustrine deposition, especially beach sand and bar sand. From the sediment lithology, sedimentary structures, paleontological features, mudstone color and local development of carbonate rock beach and so on it reflects the shallow lake environment, revealing the characteristics of dry salty shallow water lake during the fourth member of Shahejie formation deposition.In the study area beach sand and bar sand are good reservoir sands, by favorable facies analysis, combined with the reservoir thickness and physical properties of the distribution, the favorable reservoir was analysed, evaluated and predicted. Through a comprehensive evaluation of the reservoir, type of reservoir sand in the fourth member of Shahejie formation in Shaziling area is mainly the subaqueous distributary channel of delta front, beach body, bar body, beach edge, bar edge, mouth bar and distal bar of shore shallow lake.