Study On The Sedimentary System And Reservoir Forming Rules In Es₂, The Southern Part Of Shanghe Oil Field

Shanghe oil field, which located in the central uplift belt of Huimin Depression, has come into high ripe exploration phase after a thirty-year exploratory development. Summarizing the distribution of reservoirs, building reservoir accumulation model and indicating further exploration potential, can provide geology criterion for rolling exploration and development for Shanghe oil field, meanwhile, it can give reference to enhancing oil recovery in other similar oil fields.With synthetic application of high resolution sequence stratigraphy and facies controlled cycle isochronous correlation technology, both of which are delicate sequence stratigraphic correlation methods, Es2 Member in Shanghe oil field is isochronously classified and correlated. Middle-term cycle sequence correlation is mainly based on facies controlled cycle isochronous correlation technology according to indicator horizon, meanwhile, high resolution sequence stratigraphy is considered, which makes the classification plan easier explained on theory; In Short-term cycle sequence correlation, short-term base-level cycles are identified according to high resolution sequence stratigraphy. In the end, delicate sequence stratigraphic framework of Es2 Member is built according to these rules.The structure of Shanghe oil field uplifts to the northeast in a ladder-like pattern.There are many third-order faults in the region of interest, complicated by fourth-order faults. Several fault block traps are formated by both faults and structural lines, which makes structure the main controlling element of the reservoirs distribution in the researched zone. Most growth indexes of two partition faults in southern Shanghe oil field are less than 1.1 in Es2, and fault throw less than 30m, indicating relatively weak fault activity and small influence on sedimentary. Es2 Member of Shanghe oil field is deltaic environment; based on the allied facies marks, delta plain facies are divided further into three sub-facies, distributary channel, channel embankment and famada; delta front is divided further into four sub-facies, underwater distributary channel, distributary mouth bar, distal bar and underwater distributary bay. Vertical evolution pattern of sedimentary from base to top successively is described as follows, setted prodelta, delta front, prodelta, delta front and delta plain. Sedimentary microfacies distribution of each sublayer is analyzed under the control of delicate sequence stratigraphic framework. Sand bodies in the region of interest mainly are distributary mouth bar of delta front, and distributary channel of delta plain. Lower Es2 and Fourth to sixth sand sets of upper Es2 are mainly mouth bar sand bodies, with individual layer thickness of 10m, with stable plane distribution and overlapped vertical distribution. The first to third sand sets of upper Es2 are distributary channel sand bodies, with individual layer thickness of 2-3m, with unstable plane distribution.Reservoirs in the region of interest are divided into structural reservoir, lithologic reservoir and compound reservoir, which can be further divided into 5 groups and 8 subgroups, most of them are structural reservoir. Oil and gas mainly distributed in two major positive elements of plane-Shang 13 Block and Shang 56 Block horizontally, and concentrate in lower Es2 Member vertically. Controlling factors of the reservoirs accumulation are concluded, reservoir accumulation model of Es2 in southern Shanghe oil field is established, which indicates trap is the most important element that dominates further exploration activity. So the next exploration aspect is definited, fine structure research should be applied in lower Es2 and 4-6 sand sets of upper Es2, minor structural traps near to the faults and magmatic rocks should be the target; fine strata classification research should be applied in 1-3 sand sets of upper Es2, structure-lithology compound traps based on the distribution of main river channel and the study of the delicate structure should be the target. In the end, four beneficial exploration targets are proposed, with 163.96×104t forecast IOIP.