Study On The Water Intrusion Dynamic Law Of Fractured Bottom Water Gas Reservoirs

Fractured gas reservoir with bottom water is different from ordinary fractured gas reservoir, and fracture systems are extremely complex in the gas reservoir. As the formation pressure decreases in the development, the porosity and permeability decreases, which is regarded as reservoir stress sensitivity. Meanwhile, bottom water intrudes into gas reservoir along the fracture, so that recovery percent of reservoir is drastically falled in bottom water reservoir. Therefore, to carry out water invasion dynamics study in the fractured bottom water reservoir is in favour of understanding laws of water invasion, formulating effective development plan and water control measures, which is of great significance.Based on the fractured bottom water reservoir as the research object, on the basis of existing national and international achievements. Fractured cores are focused on, the indoor experimental studies of stress sensitivity and gas water phase permeability under the condition of different temperatures are carried out. At the same time, core micro electron microscope scanning analysis experiments launched is to contrast analysis of the characteristics of rock pore structure changed before and after experiments. Mathematical models are launched to describe the shape of water coning and the breakthrough time of fractured bottom water reservoir, including stress sensitivity, slip factor, skin factor. Finally, combining experiments and numerical simulation method, the stress sensitivity and the relative permeability have influence on of water invasion laws over fractured bottom water reservoir.The major conclusions of this dissertation can be summarized as follows:(1) When the core effective stress is 5 MPa, the rubber envelope is ignored over stress sensitivity experiments; Regardless of lithologic differences, stress sensitivity of fractured cores is stronger than no fractured one; Whether cores have cracks or not, stress sensitivity is gradually enhanced with the temperature rising, Which are illustrated based on the stress sensitivity experiments.(2) The core micro electron microscope scanning analysis experiments are conducted over the cores had been launched stress sensitivity experiments under high temperature(110?). Intergranular holes appear excessive compaction, the flaked illite expand in bridge type plug, willow leaf shaped chlorite narrow the circulation channel from expansion. Rock particles deform sharply, so that the original circulation channels are destroied under thermal stress from high temperature.(3) Water phase relative permeability and gas phase relative permeability of fractured cores are higher than no cracks. Meanwhile, whether cores have cracks or not, temperature has obvious effects to gas phase relative permeability, but has less impact on water phase relative permeability. When water saturation is small, the gas phase relative permeability declines rapidly with the temperature increasing, and falling range reaches57.9%-82.9%; but when water saturation exceeds isotonic point water saturation, the gas phase relative permeability declines gently with the temperature rising, which are illustrated based on the gas water phase permeability experiments.(4) The core micro electron microscope scanning analysis experiments are conducted over the cores had been launched gas water phase permeability under high temperature(100?). Clay minerals including illite and chlorite expand to block the original pore, beside holes are blocked by clay mineral and quartz. In the meantime, some particles fracture under thermal stress, part of the particles are transported in order to destroy the original channels.(5) Mathematical models are launched to describe the shape of water coning and the breakthrough time of fractured bottom water reservoir, including stress sensitivity, slip factor, skin factor based on the seepage theory of water point. Correlation curve are then plotted with Visual Basic and Matlab program, and stress sensitivity, slip factor and skin factor related to the shape of water coning and the breakthrough time are analyzed.(6) Some agreed conclusions can be drawn from the analysis of simulating water invasion over fractured bottom water reservoirs:1) The effect on gas/water ratio was little in vertical wells development way but the effect on gas/water ratio was great in horizontal wells development while the reservior stress sensitivity does exist. When gas production is less than the critical gas production, gas/water ratio increases slightly, on the other hand. The parameters including gas/water ratio, accumulated water and gas fall slightly with the increasing of the stress sensitivity when the stress sensitive coefficient is less than 0.01MPa-1, however the gas/water ratio declines shapely with the increasing of the stress sensitivity when the stress sensitive coefficient is more than O.OlMPa"1. When stress sensitive coefficient is more than 0.1MPa-1, the breakthrough time extends with the increasing of the stress sensitivity.2) The effect on gas/water ratio was little in vertical wells development way but the effect on gas/water ratio was great in horizontal wells development while the stress sensitivity is affected by temperature. The parameters including gas/water ratio, accumulated water and gas decline with temperature increasing. the breakthrough time has little influence with temperature increasing in vertical wells development way, however the breakthrough time extends with temperature increasing in horizontal wells development way.3) The parameters including gas/water ratio, accumulated water and gas decline with temperature increasing while the gas water phase permeability is affected by temperature. The breakthrough time extends with temperature increasing whether gas reservoir adopts vertical wells or horizontal well development or not.