Research To Quaternary Sequence Stratigraphy Of North Slope SanHu Depression In Qaidam Basin

Qaidam basin is located in north of Qinghai province, and it is a large Mesozoicand Cenozoic oleaginous basin ,the total acreage is about 12×104km2. Sanhu regionin east of Qaidam basin is explored and founded the Quaternary biogas, the thicknessof Quaternary strata is 3200m;the diagenesis is in low degree, high porosity and highpermeability;the sand and mud are interbeddings, sand is reservior and mud is gassource rock and cover rock;stock size of Quaternary biogas achieve 12476×108m3 ,the explored geological reserve is 1472×108m3, the third class reserve is about 3500×108m3. It is the region where founded the largest scale of biogas in the world. Sincethe nature gas has been founded in 1952, drilling is used in every structures andalmost industrial gas current or indicated wells are assembled in north slope.Sequence stratigraphy is an embranchment of geology, it is also a subdisciplineof geology which uses seismic, drilling and outcrop data to carry through strataldistributed pattern, sedimentary environments and compositive interpretation oflithofacies in order to study chronostratic framework which is cyclic, origin relatedand limited by erosion surface and conformity surface correlated with erosion surface,and interior stratum in sedimentary sequence, lithofacies distributed pattern. Sequencestratigraphy is the new development of seismic stratigraphy. It uses drilling welllogging, seismic section and outcrop to interpret the sedimentary system tracttridimensionally and each lithoface in basin , also recapitulate three dimensionalsedimentary pattern.In addition to studying different kinds of analysis, assay and test datacompositively, through the research to systemic, in-depth sequence stratigraphyanalysis and sedimentology, this passage analyses the core, seismic, logging data etc.compositively to interpret the sequence and system tract in core, logging and seismicdata, also build Quaternary sequence stratum framework in Sanhu depression andcarry through the sequence stratigraphy correlation. Basing on compositive analysisof the region structure character, palaeocurrent and according to the logging responsecharacter at different lithology section, we analyze single well facies;Studyinglithology combination of sediment, bedding and sedimentary character, in order toanalyze sedimentary environment and sedimentary character of each system tract;Comprehending analysis results of drilling(logging) single well facies andsummarizing the type and distribution of sedimentary system in whole region, inorder to discuss the sedimentary character of each sedimentary system. Basing on theregional sequence stratal framework, carry through the elaboratecompartmentalization of sequence stratum in major horizon and basing on seismicand logging data, use seismic sequence stratigraphy and drilling sequence stratigraphyto discuss isochronous stratal distributed pattern in framework. Basing on studyingsedimentary and sequence stratum correlation, foresee the advantageous oil and gasregion by combining facies and constructions.