| Yingjishu depression is located in the Easter of Tarim and exploration area amount to 15 X 104km2. There are two sets of source rock, which include Cambrian to Lower Ordovician and Jurassic. The latest resources assessment result indicated that oil-gas resources is plentiful where total petroleum resources is 2.7-3.2 hundred million tons and that of nature gas is 1.75-2.94 X 104 hundred million cubic meter. It shows that there can form middle or large oil-gas field.There is a special cover oil-gas reservoir of Jurassic in Yingnan 2 well in Yinggishu depression and its cover is fine rock scrap and deep gas source is the base of oil-gas forming. Palaeozonic has extensive source rock and the produce center of hydrocarbon is located in deep sag and the fine sandstone down direction. The Jurassic is deep gas reservation and reflected by the feature of the gas and water inversion.Sedimentary environment of the fine sandstone main includes the underwater distributary's channel of delta frontier, braid channel of flood plain in fan-delta, estuary dam, distal bar and crevasse fan. The environment of sandstone containing oil and gas includes underwater distributary's channel and estuary dam in the delta frontier. The stronger digenetic and compaction make illite-montmorillonite-chlorite clay occupying in sandstone pore and results in sandstone pore decreasing and the fine sandstone cover formed. This kind of micro-pore has high capillary pressure, and result in stratum water blocking and make the primitive permeate descend to 10-4-10-6 d class rating. So the cap rock formed.The diagenesis stage belonging to Al period of late digenetic and compression, cementation and filling are main diagenesis. The compression-decreasing amount of fine sandstone member is average for 15.95% and cementation pore decreasing member is 10.87%. The loss of pore is 26.82% due to compression and cementation. The compression deceased pore amount of oily sandstone average for 17.19%, and that of cementation is 6.13%. The pore loss controlled by compression andcementation is average for 23.62%.The main target stratum reservoir appreciation in Jurassic system relied on the II type, occupying 45 percent in stratum, the next was the III type reservoir, occupying 25 percent in stratum, The average porosity of the Yingnan 2 well producing hydrocarbon was 14.4 percent, and the average permeability was 17.73 X 10-3 um2.Later accumulation was another character of oil and gas development history in this area, reservoir diagenesis in Jurassic system controlled hydrocarbon reservoir formation in Yingjishu area. Since the middle-late diagensis period, the hydrocarbon accumulation event was effective. Jurassic reservoir experienced two main hydrocarbon migration, they were Later Yanshan period and Later Xihan period. Depth of burial condensation sandstone was shallow, so the condensation cap rock did not format, and the period was hydrocarbon ineffective accumulation period. The condensation cap rock formatted in the Later Xihan period, and hydrocarbon accumulated to be reservoir.Through the study of cap rock formation history, the sandstone cap rock of the Later Tertiary began to have the ability to cap natural gas, for another words; in that period Yingnan 2 well reservoir began to format.In the plat surface, the Longkou 1 well and the Huayingcan 1 well obviously lacked of good cap rock, so they did not format hydrocarbon reservoir. According to accumulation condition and rule in the area, forecasted that in the east of Weima 1 well and in the north of Longkou 1 well and Hueyingcan 1 well and in the east-south of Yingnan 1 well etc. area were prospecting hydrocarbon reservoir distribution area.On basis of above studies, the accumulation factors of natural gas, cap rock, reservoir, diagenesis and pore-forming evolution, combing with the natural gas migration and accumulation. The model of accumulation and diagensis in the area of Yingjishu depression on Jurassic is established, the depression belongs to the control of hypogene break-cov...
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