| Recently, district6-7is the main water-flooding reservoir in Tahe oilfield, and it is also the national technical research demonstration area of water-flooding well group. This thesis studied the scheme and mechanism of water injection, of which difficulties are obvious. Firstly shape of fracture and vuggy is very complex, secondly the geological model cannot be precisely reflected by geological methods such as seismic and well logging. Thirdly geological method fails to describe the key geological element for water performance, and lastly reservoir engineering analysis will lead to multiple solutions.Therefore, based on literature review, it is analyzed the oil and water flow character, dual flow mechanism and production performance in vug, fracture-vug and fracture reservoirs. Meanwhile, the geology situation and production performance are combined by geology modeling and numerical simulation, which is taken as an effective method to study the water-flooding of district6-7reservoir. According to the water cut of the water injection efficient period, steady period and modification period, the injection scheme is simulated and injection parameters is optimized to provide a technical reference to further understand the water-flooding of fractured-vuggy reservoir. The main results are as following:(1) The water injection mode of each typical unit:the optimized water injection combination of main fracture typical unit is first mild continuous water injection, then mild continuous water injection and finally the cyclic water flooding; secondary fracture typical unit is the cyclic water flooding during the whole process; epi-karst typical unit is first mild continuous water injection, then the cyclic water flooding and finally impulse water flooding; underground river karst typical unit is first large displacement continuous water injection, then mild continuous water injection and finally the cyclic water flooding.(2) Through the method of numerical simulation and the analysis of water injection practical experience shows:1) Three injection mode parameters of main fracture typical unit are optimized as:during efficient period the range of continuous water injection intensity is80-150m3/d, and injection-production ratio is1.5-3.0. During steady period the range of continuous water injection intensity is50-100m3/d, and injection-production ratio is1.0-1.5. During modification period the intensity is50-80m3/d, and injection-production ratio is about0.9, of which conventional cyclic injection period is45days including15days injection and30days well shutting up.2) Three injection mode parameters of secondary fracture typical unit are optimized as:during efficient period the range of water injection intensity is80-120m3/d, and injection-production ratio is1.0～1.25, of which conventional cyclic injection period is105days including45days injection and60days well shutting up. During steady period the range of water injection intensity is40-100m3/d, and injection-production ratio is0.65-1.0, of which conventional cyclic injection period is90days, including30days injection and60days well shutting up. During modification period the intensity is40-80m3/d, and injection-production ratio is0.6-0.8, of which conventional cyclic injection period is75days including15days injection and60days well shutting up.3) Three injection mode parameters of epi-karst typical unit are optimized as:during efficient period the range of continuous water injection intensity is150-200m3/d, and injection-production ratio is1.5～2.5. During steady period the range of continuous water injection intensity is100-150m3/d, and injection-production ratio is1.0～1.5, of which conventional cyclic injection period is75days, including60days injection and15days well shutting up. During modification period the impulse injection is100-200m3/d for every30days and shut well up for the same period.4) Three injection mode parameters of underground river karst typical unit are optimized as:during efficient period the range of continuous water injection intensity is250-350m3/d, and injection-production ratio is2.5～4.5. During steady period the range of continuous water injection intensity is100-150m3/d, and injection-production ratio is1.0～1.65. During modification period the intensity is80～150m3/d, and injection-production ratio is1.0～1.5, of which conventional cyclic injection period is75days including60days injection and15days well shutting up. |
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