| The fractured reservoir is a most difficult one in the course of oil-gas exploration and development. Nowadays, it still be a forward project, for it synthesizes rock mechanics and fracture spaces. The fracture-pore type reservoir puts challenges to its protection, because the existing state of fracture has complexity and variety. With the rapid development of modern petroleum industry, the important point of exploration and development not only has to divert to some more difficult reservoirs, such as fractured reservoir, especially low-permeability reservoir and so on, but also is growing increasingly. According to incomplete statistics, the proportion of fractured reservoir in the petroleum reserves as a whole is about 50%. The fractured reservoir is the best one in economic performance in the whole world, and because its fracture gives a good seepage passageway to well hole. However, people found that its output actually don't achieve the prediction value after some fractured reservoirs were drilled and completed. Obviously, this is because the formation polluted by drilling working fluid and the fracture deeply plugged by drilling working fluid cause flow resistance to be added. For this reason, studying the fracture-pore type reservoir protection has a important and profound realistic significance.This study uses multi-specialty and multi-subject theory that include: clay mineralogy, petrology, lithology, organic chemistry, inorganic chemistry, reservoir geology, physical chemistry.colloid chemistry, reservoir physics, hydromechanics, seepage mechanics, rock mechanics, and drill technology, cementing techniques etc. By means of laboratory experiment, mathematic method, computer programming etc, taking the study of sensibility of fracture to stress path, well fracture width prediction, formation damage mechanism, temporary plugging mechanism etc as key pints, this thesis reveals the mechanism of fracture-pore type sandstone reservoir protection, and optimizes the drilling working fluid(DWF -drill-in fluid and cement slurry) system of protecting fracture-pore type reservoir, and also conducts guide site testing, contrast site testing, and industry site testing, and at last forms an advanced and practical DWF system for fracture-pore type reservoir protection.By the study, this thesis attains four creativity achievements as follows. The first is the study of fracture closed law under the condition of well stress, the evaluation and verification of fracture closure estimation models, the derivation and verification of well fracture width prediction model, and the practical prediction of fracture width in the study area. The second is the analysis of fracture-pore type reservoir damage factors, the exploration of fracture-pore type reservoir damage mechanism, and the establishment of physical and mathematic models on the damage of DWF to fracture flow capacity and fracture-pore bound. The third is the study of fractured reservoir temporary plugging mechanism, the establishment of physical and mathematic models, the description of the quantitative relation of bridge distance distribution functions with fracture and particle parameters. The fourth is a DWF system fitting for fracture-pore type reservoir protection.The results of in-site testing indicate that: a. the less error of established well fracture widthprediction model could entirely meet the needs of engineering; b. the attained drill-in fluid could effectively protect fracture-pore type reservoir, i.e. the skin factor decreased 107.6%~ 116.7% and the single-well output increased 42%; c. the optimized cement slurry had had a good reservoir protection effect, i.e. the mean oil output and the mean gas output increased 8.72% and 8.83% respectively; d. the DWF system was wide and practical, and it not only fit for general exploratory wells and development wells, but also fit for complex science-exploration wells.
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