Well Logging Evaluation On The Carboniferous Volcanic Reservior In Chepaizi Area

Chepaizi is located in thrust fault zone in the northwestern margin of Junggar basin.The basement is Paleozoic carboniferous volcanic rock.Due to the particularity of volcanic rock,there are a lot of problems in the research: the lithology of volcanic rock is complicated;the reservoir space is various;the volcanic rock-electricity relation is still not clear;and the reservoir physical property parameters are difficult to calculate.For these problems,we mainly use well logging data to carry out the analysis of characteristics of volcanic rock lithology and reservoir space,the study on the volcanic rock-electricity relation,the establishment of logging calculation model of reservoir parameter and the reservoir evaluation standard.The following results are achieved:(1)Assured that there are mainly 6 lithology in the study area: basalt,andesite,basaltic andesite,basaltic brecciated lava,basaltic breccia,and tuff;There are mainly 3 kinds of reservoir space: primary pore,dissolution pores and cracks,and 3 kinds of reservoir space combination.(2)Expounded the volcanic rock-electricity relation: lithology is the main factor influencing logging;DEN,CNL and AC have good correlation with porosity of different lithology;Contrast with dry formation,the logging response indicate that there are much more reservoir spaces and DTST increases more sharply caused by attenuation of the array acoustic logging in oil reservoir.(3)The logging porosity calculation model of different volcanic rocks were established.The test results indicate that the multivariate linear regression method is the best in a variety of methods,and the average relative error is 10.2%.Compared with the previous interpretation results,the relative error decreased by 34.9%.According to the reservoir unit,the reservoir is divided into three types,and get three calculating formulas of matrix permeability.The average relative error is 37.4% which decreased more than by 300%.(4)Proposed the volcanic reservoir classification standard in Chepaizi area.According to the porosity,permeability,effective thickness,and imaging logging response,the volcanic reservoir is divided into three kinds.Predict the reservoir distribution of the volcanic rock.In one single fault block,the best reservoirs locate in high structural position and the position nearby the major fault;the closer to the Changji oil source area,the more reservoirs development.