A Study On Reservoir Evaluation Of The Chang 6₃ In Baibao281 Area

The study area of this paper is the Baibao 281 area, which is located in the west of Shanbei Slope Belt in Ordos Basin. In totally, the Baobao 281 area shows the pitch structure westward. And on the basis of the structure, the Baobao 281 develops a series of nose like structure, which were caused by the differential compaction. The target layer is Yanchang Formation sixth phase in Upper Triassic, that is one of the most important oil bearing layers in Ordos Basin, whose oil-pool type is lithology-strata oil pool. On the basis of the cycle of sedimentation, the author combines the regional geology and regionality marker bed, and then builds up section profile in the study area. At the same time, according the well line and well logging, the author detailedly divides and compares the strata. And the author utilizes the result of the core observation, thin section identification and the data of grading analysis, combines the electrofacies analysis. On the top of that, the author studies the law of the sedimentary facies in plane. Afterward, directeing by the theory of the sedimentation and reservoir geology, the author overall utilizes the core and the thin and mercury pemetration, studies the reservoir physical property and the characteristic of pore configuration. And then using poroperm characteristics and the top of it, the author studies the aeolotroprism of interlamination, intraformational and flat. Finally, combining the law of hydrocarbon accumulation, the author establishes the classification evaluation criterion and forecasts the favor and the less favor accumulation facies belt .On the basis of the data of single well, the author straightens out, digests and sums up the report of investigation, studies the reservoir characteristic with availability well drilling, coring, well logging and testing, etc. In the research method, the author adopts the convention pool description technique. In mapping technology, the author adopts the mapping analysis software such as Carbon, Geomap and Discovery, synthetically studies the reservoir.The study found that the Oil layer in Chang 63 is divided into three small layers from bottom to top: Chang 633, Chang632, Chang631 small layer. Chang 63 oil layer is the lake slump turbidite fan deposits in delta front, whose sedimentary subfacies is majpr middle fan and outer fan, the sedimentary microfacies is major braided channel. The sand body in the study area is more development. In horizontal, the connectivity of the Chang 632 and Chang 633 small layer sand body is better. In vertical, the study area develops several sand bodies, which is overlapped and reflects the slump overlay in many times. In plane, the whole sand body distribute from NE to SW. And the sand thickness and distribution patterns are controlled by sedimentary facies. But the reservoir physical property is totally poor. The average value of the porosity is 10.72%, the average value of the permeability is 0.288×10-3um2, and the average value of the oil saturation is 42%. So the author believes that the reservoir physical property is low porosity, extremely low porosity and super low permeability. The aeolotropism of reservoir is serious. The srength order of the aeolotropism is Chang631, Chang632, Chang633. On the basis of sedimentary microfacies, reservoir physical property and the plan distribution of the sand body, the author establishes the criterion of the reservoir classification. And then the reservoir in the study area is divided into four types: typeⅠand typeⅡhave more better infiltrating fluid capability of the reservoir, type III is less better, type IV is non-reservoir. And then the author overall evaluates the Chang 63.The typeⅠis most important in the study area, which distributes along northeast to southwest. The typeⅠdistributes around the Bai240-Bai453-Bai254 area. The space is large and the contiguous nature is good. And the reservoir physical property is good and oil saturation is high. The storage capability and infiltrating fluid capability are strong. The daily output of the single well is high. So the author believes that the area is concentrated area which is Stable and high yield. The less favor reservoir is typeⅡ,which is located the Bai473-Bai460 in the west of the study area that distributes band and the space is small.