Well Logging Evaluation Of The Judgment About Effectiveness Of Carbonate Reservoir

As we know, large amounts of oil and gas, with more than60%share of global production, are being pumping out from carbonate reservoir of many great oilfields and high productivity wells all over the world. The difference between clastic reservoir and carbonate reservoir is that the carbonate reservoir has too many anisotropic fractures and dissolved caverns of space. Various pore structure and fierce maldistribution make well logging evaluation of carbonate reservoir be the one of the great challenges in well log interpretation. Effectiveness of carbonate reservoir also takes an important role of well logging evaluation of carbonate reservoir. Only by identifying effective reservoir from the vertical aspect, we can distinguish reservoir fluid, calculate the deliverability and indicate the resource of the reservoir. Therefore, it is meaningful that study on effectiveness of carbonate reservoir.The target reservoirs of this thesis are located in Ordovician carbonate reservoir in the Tarim basin. Because of inhomogeneous and multiple reservoir pore spaces and short detection range of well logging instrument, the judgment about effectiveness of carbonate reservoir needs diversified logging devices with different detection range and a large quantity of stratigraphic information. Research Ideas of this thesis are concluded based on research:(1) To differentiate the type of carbonate reservoir by studying the characteristic feature of various pore structure and fierce maldistribution.(2) To qualitatively evaluate the effectiveness of inhomogeneous carbonate reservoir by analyzing plentiful information from well test and logging devices such as FMI, conventional logging suite, array sonic tool and far deterctor.(3) To quantitatively predict effectiveness of carbonate reservoir and classify the grade of carbonate reservoir with most influential reservoir parameters selected and used.Relatively logical methods to judge the effectiveness of inhomogeneous carbonate reservoir are proposed based on the research ideals above, we can make conclusions as follows:(1) The effectiveness of pored carbonate reservoir is more influenced by the type of pore.Because of the impact of deposition and diagenetic change, reservoirs with various lithologic character have different kinds of pore type.(2) The effectiveness of fractured carbonate reservoir depends on open gap, infillings and the extension of fractures. The largely fractures open and further fractures extend, the better effectiveness is.(3) The effectiveness of vugular carbonate reservoir is determined by growth of vugh. Big radius, more openings in area and favorable connectivity make it good effectiveness.(4) The compound mode of fractures and vuggies is very important for the effectiveness of fractured-vuggy carbonate reservoir. the effectiveness of reservoir with fracture face dissolved and good connectivity is better than the one with bad connectivity.(5) We should study the fillers in cave and ascertain how the caves are filled up, for they concern the effectiveness of reservoir. It is stated that the effectiveness of reservoir with argillaceous ingredient filled is worse than others.(6) Bond index M, calculated with three porosity model, is used to measure the tortuous extent of electrically conduct of carbonate reservoir and indicate the geometric alteration of pore space. The bigger Relative porosity of communicating interstices is,the smaller value of M will be and the effectiveness of reservoir is also better.Though these estimating methods of the effectiveness of carbonate reservoir succeed in well logging evaluation of Ordovician carbonate reservoir in the Tarim basin to some extent, quantitatively predicting effectiveness of carbonate reservoir and classifing the grade of carbonate reservoir have their limitation because of plenty of operational information and data from conventional logging suite with small investigation radius. For the next job is that we need to solve inversion problem of far deterctor so that more reliable information can be acquired from far deterctor to help the abundance and improvement of the quantitative predicting methods of effectiveness of carbonate reservoir.