Formation Mechanism Of Effective Reservoir In Es_3-4 Of Wendong Area In Dongpu Depression

With the advance of the shallow oil exploration and the situation that oil demand exceeds supply, the orientation and target has changed to the deep zone currently. And there are lots of hydrocarbon reservoirs in the deep zone. The reservoir bed in Es_3-4 of Wendong area in Dongpu depression has good collecting condition, but no hydrocarbon reservoir is found. So the key is the reservoir research.With the Es_3-4 reservoir of Wendong area in Dongpu depression as the target, we researched the formation mechanism of effective reservoir using core observation, cast thin slice, X ray diffraction, physical property analysis, mercury penetration, fluorometric analysis and cathodeluminescence.There is lake delta front subfacies in Es3, and the lithology is feldspar-porphyry sandstone and feldspathic quartzite. There is density current depositional system in Es₄, and the lithology is feldspathic polylitharenite and lithic sandstone. The litho is fine, well sorted, mid-rounded, grain supported and pore cemented. The primary accumulating space in Es3 is emposieu, and that in Es₄ is fracture. The reservoirs are low-porosity and low-permeability. The distribution of the physical property is affected by the sedimentary facies. There are four abnormal pore developed zones vertically. The lower property of oil layer is 12%, 1×10^-3 m2. And the lower property of gas horizon is 8%, 0.1×10^-3 m2. We divide the Es_3-4 reservoir of Wendong area in Dongpu depression into three kinds according to the physical property, pore throat structure, pore style and storage ability. There are lots of kinds of diagenesis in the region of interest. The primary diagenesis is coMPaction, cementation and denudation. The primay cement is carbonate and gypsolyte. CoMPaction and cementation are harmful to the physical property. Denudation increased the physical property. The Es_3-4 is in the middle and late diagenetic stages. There are lots of contributing factors of the effective reservoir, for example, the depositional environment,the tectonic activity, diagenesis, hydrocarbon feed and gypsolyte with the abnormal pressure. According to the effect of the diagenesis to the porosity evolution, we resume the history of the formation of the reservoir in Es₃², Es33-4 and Es₄. We build 3 genetic models of the effective reservoir: denudation, hydrocarbon feed and gypsolyte. We forecast the effective reservoir of Es₄ is under the Es₃⁴ gypsolyte. The effective reservoir of Es3 is under Es₃² gypsolyte and in the vicinity of faults.