Study On The Sediment And Reservoir Character Of Xingouzui Formation In Xiefengqiao Area Of Southwest Edge Jianghan Basin

The factors of hydrocarbon accumulation of Xiefengqiao area were very complex. The3D seismic data in hand could not further meet the requirements for comprehensive research, in the aspect of fault accurate homing and recognition of reservoir body. But the resource extent in this area was979×104t, trap reserve was752.7×104t, and proved reserves was less than100×104t. The proved rate was only20percent. So there had great resources exploration potential in this area.There are several problems in the cognition of reservoir characteristics of Xiefengqiao oil field:(1) Low resolution of seismic data had bad influence on precision of reservoir prediction and reliability of secondary faults interpretation.(2)Lacking of study on reservoir heterogeneity, it could not have full cognition of the lateral variation of reservoir and prediction on the favorable reservoir zones distribution.(3) The lack of identification standards to distinguish oil and water layers and the inadequate study on controlling factors of reservoir spatial distribution of oil-gas gathering zone affect determination on the oil-water boundary.(4) In order to confirm economical and effective development mode and method, oil and gas reserves yet to further be determined under the increase of data.Taking full advantage of analysising technology and visualization technology in3-D seismic data fine interpretation technique, combined with data of core, logging curve, and grain size, point-line-surface and layer-segment-group integrated, it studied tectonics, sedimentation, reservoir characteristics in Xiefengqiao area. The series of the achievements were:(1) The oil-bearing formation Ⅰ and Ⅱ in Xin’gouzui group in study area belonged to shore-shallow lake subfacies. Beach sand was primary favorable facies belt, and the sand body spreads parallelly along the shore. The secondary was rip current channels(X1well obtained industrial oil flow), which spreaded perpendicular to beach sand body. Oil-bearing formation Ⅲ belonged to turbidity current deposits. Turbidity current channel and output fan turbidite sand were favorable facies belt. At the later sedimentary period of oil-bearing formation and sedimentary period of oil-bearing formation III,water body was occlusive. In this area, well block X4, X3, and X6developed enclosed sendiments gypsum-mud.(2) Problems about parent rocks provenance:The content of quartz and feldspar in the detrital mineral was high, and the cuttings composition was little in rocks. The main lithology was the acidic eruption rock, and little was phyllite. Heavy mineral combinations were tourmaline, zircon and magnetite. The results of comprehensive analysis showed that the parent rocks of Xin’gouzui group mainly came from granite and acidic eruption rock, and a small amount form phyllite.(3) The component content of cement in sandstone reservoir had a controlling function on oil and gas accumulation:In the sandstone which had hydrocarbon show, content of calcite was below10percent in most cases, and was15to16percent in a few cases. The content of anhydrite almost was from0to4percent, and minority was from8to14percent. The content of interstitial material almost is less than17percent, and minority is18to22percent. In the sandstone which has no hydrocarbon show, the content of calcite was more than15percent, content of calcite was more than15percent, and the content of interstitial material was more than20percent.(4) The assemblage characteristics of interstitial material also had controlling affection on oiliness of reservoir stratum. Type Ⅱ (X8and X7well) and type VII (X5well) were superior to other various types, because of the development of chink dissolved pores and intragranular dissolved pores. In the type V, when the carbonate rocks occur the dolomitization, the volme reduces. Then, the calcite has a shape of plaques.The oiliness of type V also is superior than other typies.(5) Relative content of carbonate and clay in interstitial material was the controlling factor for the development of dissolved pores. When the content of carbonate was more than clay, the dissolved pores would develop (type Ⅱ). But the fillings of calcite could worsen dissolved pores in interstitial material (typeⅢ). When the content of interstitial material was high and the dolomite and calcite compactedly filled, property of oli and gas became worse(type Ⅳ).