The Research Of Geoburried-hills Reservoir Identification And Prediction In CheXi Area Of JiYang Depression

Various kinds of reservoir space such as pore, cavern and fracture are existing in carbonate buried hill reservoirs, however, for their complicated genesis and strong heterogeneity, it's very difficult to identify and predict the characteristics and regularity of those reservoirs. Combining with theories of sedimentary petrography, structural geology, reservoir geology as well as logging and seismic data, carbonate buried hill reservoirs in studied area have been identified and predicted and their reservoir space characteristics have been described. Then this paper analyzed reservoir space characteristics and their controlling factors, built a geologic model of buried hill reservoir, explored their forming mechanism and analyzed reservoir distribution regularity, which aims at predicting favorable reservoirs. The major results have been achieved in the following aspects: (1) Under the affection and reconstruction of multi-factors like sedimentation, diagenesis and structure, various types of reservoirs, such as weathering crust cast type common in buried hill, laminated pore and cavern type in inner buried hill,faulted denudation nearby the fault and fractured type in the structure axial region, are formed in the carbonate buried hill; (2) Well-logging geologic characteristics unit, well-logging unit in short, that is stratigraphic intervals with analogous geologic characteristics, has been introduced in this paper. 4 types and 11 subtypes are classified by using imaging, curve and numerical characteristics and a typical model of well-logging unit identification has been build. Then in combination with regional geological settings of Chexi area, four types of buried hill reservoir space, such as fracture related to both folding and fault, pore and cavern related to both unconformity dissolution and lateral denudation of the fault are divided and those logging unit characteristics are then researched. At last, the distribution characteristics of reservoir space in both vertical and planar directions of different types of buried hill, as well as three major factors affecting reservoir development, lithology, structure and denudation, have been ascertained. (3) The structure form of buried hill has been confirmed through precise calibration and pre-stack depth migration processing of seismic data, and by means of co-utilized constrained inversion processing, energy absorption characteristic analysism, seismic attribute analysis, seismic facies analysis and etc., a comparably reliable effect of buried hill reservoir has been achieved. (4) The distribution regularity of buried hill reservoir in Chexi area is analyzed according to geologic, logging and seismic data, and the results show that planar distribution characteristics of buried hill reservoirs are as follows:â‘ Weathering crust cast reservoirs are common developed;â‘¡Weathering crust cast is not strict in lithology and stratigraphic position;â‘¢Tthe distribution of effective reservoir in weathering crust cast belt is controlled by inverted fault;â‘£Stepped fault has controlled the favorable reservoirs in inner buried hill. In the vertical direction, the distribution of reservoirs is relatively complicated. Reservoir evaluation suggests best reservoirs in Fengshan Formation, Yeli-Liangjiashan Formation and Badou Formation while secondary ones in upper and lower Majiagou Formation. All of above work shows favorable buried hill reservoirs in studied area. In south gentle slope, reservoirs are well developed in the structural high part of uplifted wall of inverted fault while lower Paleozoic residual hill secondly; Whereas in north artic region, weathering crust reservoirs developed well in the structural high part of second-step buried hill, inner buried hill reservoirs preferred to exist such areas as second-step fault with strong activities.