Characteristics Of Reservoir And Regularity Of Petroleum Distibution In Daerqi Oilfield

The characters of structure in Daerqi area show different zones from north to south and from east to west. The main oil-bearing formation is the Tenggeer formation in the lower Cretaceous period. Other bed in which has Less oil is the 1^st member of Duhongmu formation. The both layers are what we want to Research on.The basin is a Mesozoic fault subsidence residual one in Daerqi area, in which develops many kinds of sedimentary facies and presents complex characters. No matter from Longitudinal or landscape orientation, the facies changes fastly. Duing to different object sources and disequilibrium tectonic activity, the facies have the following characters proximal object sources, multiphase, fast deposition, narrow facies zone and changequickly. On the basis of this area's structural evolution and depositional setting, the depositional patterns of the Tenggeer group and the 1^st member of Duhongmu formation are built up. And from study three depositional system-alluvial fan, braid delta and lake are concluded. In which develops two important turbidite sandstone, deep-lake fans sandstone and slump turbidite fans sandstone. From the distributing graphs of the sedimentary microfacies of the sand I layer, sand II layer, sand IIIlayer of the 1^st member of Duhongmu formation and the Tenggeer group, and also the overlap of them, the development of sand is controlled by the transitional facies of the alluvial fan-braid delta-lake, which has effect on hydrocarbon distribution.In this area, the reservoir's contributing factors are diagenesis and sedimentary facies. The thin sections analysis show that reservoir's main space is secondary porosity in the Tenggeer formation and the 1^st member of Duhongmu formation. According to the improvment to reservoir or not, We classify the diagenesis into two kinds: constructive action and destructive action. Constructive action that mainly contains destabilization detrital component catagenesis, denudation and cataclasis, which are also the significant factors for the reservoir's improvement. And denudation and cataclasis are two key factors. Distructive action that mainly contains compaction, replacement and secondary enlargement, which are adverse factors for improving reservoir's quality. Studying the control of sedimentary facies, the reservoir developed in shallow lascustrine sand bar and deep-lake fans that have better physical property, and the sheet sand and deep-lake sheet sand taken second place.Because of little effect of paulopost faults on deposition, the reservoir's development is mainly under the control of depositional system of alluvial fan-braid delta-lake transitional facies, which also have effect on the reservoir's physical property. And with matching the hydrocarbon generation of source rocks time and trap's forming time, this type depositional system also control the petroleum's distribution. As a whole, along the slope, there are three petroleum zones across NE—SW: higher faulted anticline petroleum zone, middle lithologic-structural petroleum zone and lower structural-lithologic petroleum zone, of which the distribution is different in west and east area. From mentioned above, subtle reservoir formation is the most favorate target for exploring in the lower structural-lithologic petroleum zone, such as turbidite sandstone and shallow lascustrine sand bar.As a whole, the high production wells of Daerqi oil field commonly surround the slope's lower location to deep concave in the meare-deep lake. And the high production wells usually develop in the favorate microfacies such as turbidite sandstone and shallow lascustrine sand bar and so on with better physical property, near oil sources, deep bury and little damage.Under the tectonic setting of west area of Daerqi, high production wells concentrate in Tenggeer formation, which is also the petroleum enrichment zone.In the deep lake sedimentary environment, the oil source is adequate with higher maturity and better type of organic matter near the concave because of the high seal of faults. The step of low slope near the concave, especially the first and the second step of the Tenggeer formation, is the favorite exploring area owing to adequate oil source, weak tectonic uplift, little damage and good conservation.