Research On The Reservoir Characteristics And Forcasting Advantageous Regions Of The Chang8Formation In Maling Area,Ordos Basin

This paper aim at the reservoir of Chang8in Maling district of Ordos basin, with the direction of geological statistics, reservoir sedimentology, logging geology and sequence stratigraphy theory and on the base of collecting plentiful data of logging, drilling, core description,well testing and early production, also adopting various kinds of experiment means in light of casting film, electron microscope scanning, hydrargyrum driving test, X-diffraction, grain size image and rate-controlled mercury penetration which is one of the advanced measuring methods at present. Widely absorbing the previous research results, following the principles of static and dynamic data combination and systematic treatment with subject. As an innovative outcome,the paper study the provenance paleocurrent direction, distribution regularity of sedimentary facies, reservoir microstructures in depth and characterized the degree of reservoir heterogeneity and variation from semi-quantitative to quantitative and analyzed of the controlling factors of reservoir development comprehensively and drawn favorable block prediction. All those study are to provide geological base for the following adjustment of exploitation project.This dissertation integrated with background of areal geology and electro-facies analysis, according to core observation, grain size image,also applied Variogram analysis,it shows that the study area belongs to front-delta facies, the source directions and palaeo-current come from the southwest and northeast, and appears the process which the level of the lake gradually rising, hydrodynamic energy waning, the accommodation space increasing in the sedimentary evolution, we called it retrogradation,and the stratigraphic framework is built.The core of this paper is to study the ultra-low permeability reservoir property and heterogeneity of study area from macroscopic to microscopic features synthetically. The microscopic heterogeneity of Chang8reservoir is mainly controlled by throat distribution characteristics, the pore throat’s contribution to the reservoir microscopic heterogeneity are more than pore’s in the reservoir development, and make more contribution to the mercury saturation. The pore-throat ration of the low permeability reservoir is more than the higher permeability reservoir’s, it also has the wide distribution range,small throat and serious jamin effect with the oil well without natural capacity, the early production declining quickly, may be it due to the much of residual oil distribution in the pore-throat, so it should be took corresponding measures in the early production in time.Reservoir heterogeneity model is established according to the sedimentary facies belt, interlayer and in layer heterogeneity characteristics. The sand body of underwater distributary channel also have more stronger reservoir heterogeneity,distributary bay which deposited thin layer with argillaceous increasing, heterogeneity of the sand body is relatively weak. It characterized of reservoir macroscopic heterogeneity with traditional geo-statistics and lorentz curve methods, it shows medium to strong heterogeneity of chang8reservoir on the whole.The main controlling factors of the reservoir in this area are the lithology characteristics, distribution regularity of sedimentary facies, diagenesis and tectonic fracture. The water injection has strong effect on the reservoir modification and heterogeneous of reservoir overall. Considering the influence and contribution of various factors to the reservoir, selected reservoir lithology, physical property, oiliness, heterogeneity parameters and so on, combined with formation test and production test results, it make the evaluation and prediction for the favorable target area with the fuzzy mathematics method.