Study On The Damage Mechanism Of Stimulated Reservoir Volume Of The Tight Gas Reservoir

Tight gas is the most realistic unconventional gas, and it will become the important resource for the rapid and stable development of natural gas industry in China. However, tight gas mainly occurred in tight sandstone with low porosity and low permeability, which needs fracturing technology to get industrial gas flow. At present, Stimulated Reservoir Volume becomes the effective method by comprehensively transformation and increasing seepage area of reservoir. But in the fracturing process, not only can the fracturing fluid help to improve the seepage passage of oil and gas, but also can bring a variety of damage to reservoir. In this paper, the cores of tight gas reservoir in a certain area are studied by laboratory physical simulation experiments. From these, not only can we achieve the damage mechanism of tight gas reservoir by the fracturing fluid, but also get the influence of different amount of liquid on the damage mechanism of fracturing fluid, and the main damage mechanism of different anti phase, which have some guidance function for the application of fracturing fluid in the actual process and the optimization of the fracturing fluid formulation. The main research results are summarized as follows:1. The geological features of the target reservoir were studied by X-ray diffraction (XRD), the scanning electron microscope (SEM) and the constant rate mercury injection technology. The results show that, the pore of target reservoir cores is not developed well in general and has a small amount of intergranular pore. In addition, the content of clay minerals is medium in general, the main cements are kaolinite and other clay minerals are relatively small. Besides, effective throat radius of target reservoir is small.2. Through ordinary flooding experiments and NMR technology, adopting the parallel comparison method, it quantitatively analyzes the correlation of water sensitivity damage and water absorption of clay, water lock damage and fracturing fluid holdup, and the dynamic changes of water sensitivity damage and water lock damage, so does the solid damage. The results show that the water sensitivity and solid damage is irreversible and unrecoverable damage, while water lock damage is a dynamic process, at the initial stage of gas back row, water lock damage is very large, but with anti pore volume increased, water locking damage has been very good released. Eventually the water locking damage is very small.3. Through the conventional displacement experiment, and parallel comparison method, it studies the influence of water sensitive damage, water lock damage and solid matrix damage by different squeeze liquid (1,5,10PV). The results of the study indicate that the volume of squeezed liquid has a little effect on the water lock damage, and almost has no influence on solid damage,while has a large impact on the water sensitivity damage. At the early stage of gas back row, water lock damage is the main damage, but with the squeeze fluid volume increased, water sensitivity damage increased significantly, so the water sensitivity and water lock damage have become the common initial major injury; at anti later, water sensitivity damage has always been the main damage mechanism.