Subtile Sediment And Sequence Character In Northeastern Sichuan Basin

The upper Triassic xujiahe Formation in Sichuan basin is the the popular, key exploration horizon of Mesozoic terrestrial strata.80s, with the quickening pace of exploration, sichuan basin has found Yuanba, longgang, Heba, Puguang,Xinchang, ShuNa and other large gas field, the terrestrial gas reservoir is mainly Xujiahe and Ziliujing Formation.Compacted sandstone reservoirs of xujiahe formation is the main reservoirs in Sichuan basin, lithologic-structural trap gas reservoir is main gas reservoir type, gas reservoir distribution in different areas of the messy, the difference of reservoir forming background conditions, and gas reservoir depth greater and so on various factors that restrict the exploration and progress of xujiahe reservoir.In recent years, China petroleum and Sinopec concentrate superior power, through the seismic, logging, geological exploration and so many kinds of research methods and carry out large-scale exploration and research work for Xujiahe Formation in sichuan basin, they learned a further information about the distribution characteristics, sedimentary background, hydrocarbon generation condition and the reservoir rock characteristics of Xujiahe formation. Petroleum geologists know not only two section has greater potential for exploration, three and four sections also have same potential for exploration. In the near future, three sections of the lake facies reservoir sand body in Jiulongshan area take big breakthrough when gas testing, four sandstone reservoir rock learn the research results of the characteristic that its good prospect in oil and gas exploration.This thesis mainly integrated application of drilling, logging, core, outcrops and seismic data, and carry out the northeastern sichuan area xujiahe stratigraphic division and correlation, establish the integrated sequence stratigraphic framework; In the sequence stratigraphic framework based on research, in combination with drilling material, we carried out the xujiahe single well deposition facies division and correlation, determined its vertical and horizontal distribution; Combined with seismic data, we determined the distribution of facies; Establish northeastern sichuan area xujiahe depositional model and clear favorable facies belt and the spatial distribution of cloth predicting favorable sand body distribution area; Through the careful research, we conclude that:1、xujiahe formation is divided into six members, the source-atrophy and lake-expanding period is X1, X22,X3and X5, forming a set of primarily sea (lake) mudstone stratum, is the area of the favorable hydrocarbon generation layer and cover layer; X2, X4, X6is the period of source-expanding and lake-atrophy,forming a set of continental or sea land transition phase sandstones;Bcause of the control of construct,X6strata often disappears in north and north-west Sichuan Basin;The structure of study area is flat,near the mountin,wo often found the obvious spectrometry uplift trace.2、Overall, xujiahe formation is divided into SQ1, SQ2, SQ3, SQ4four sequences, each sequence is lack of lowstand systems stract, SQ1highstand systems stract are formed by three parasequence sets, SQ2and SQ3highstand systems stract consist of two parasequence sets, sand body in study area mainly focus on highstand system tract, sand body in part of the layer development in early highstand system tracts.3、Except for the north west and north east material sources, the south material source may exist; Northwest largest material sources, north west material sources is the main material sources, then is the south material source, north east material source is the least.4、Tide-influenced estuary is the main sedimentary environment in X1. the braided fluvial river delta front sedimentary system is the main sedimentary environment in X21,braided river underwater is the main reservoir types. shallow lake sub-facies is the main sedimentary environment in X3,flood river is the main reservoir. fan margin phase is the main sedimentary environment in X4.,gravel quality deposition and braided river is its main micro phase, braided river is relatively favorable reservoir facies belt.5、We think that sedimentary background controls reservoir rock type and size; Sediment source and the different sedimentary environment is good to form a variety of reservoir construction-facies, the reservoir-built facies is braided river under water horizon consists of lithic sandstone and feldspar sandstone,the bar consists of quartz sandstone, the flood river consists of calcium crumbs sandstone; At the same time sediment source, water power control the reservoir rock particle size, the larger rock particle size which pore preservation condition is perfect. Many reaserch results are good for exploration and prediction,we found the thickness is biggest in northwest area (porosity is greater than5%) and the reservoir pore developments well, northwest area is the most favorable exploration target.