Feasibility Study On Acidic Pressure Of Sealing Sandstone Reservoir

The target block is a typical fractured tight sandstone reservoir, which characterized by ultra-deep, ultra-high pressure, ultra-high temperature, thick reservoir, low porosity, and low permeability and natural fractures filled or half-filled by calcareous. Complicated geological conditions cause long well construction cycle and great investment. Only by maximizing production per well can achieve efficient development of gas reservoirs. However due to heavy pollution from drilling the normal production is limited. It is often needed to carry out stimulation to achieve its geological proration requirements. Previous measures in the target block are usually matrix acidizing, which cannot effectively remove deep pollution; There are also some small-scale hydraulic fracturing, which the production increases2-3times showing great production potential. However there are some characteristics in construction process, such as high operating pressure, difficulty in filling sand. In order to solve difficulties in fracturing tight sandstone reservoir, this paper proposes a new stimulation ideas-volume acid fracturing, and through simulations and laboratory experiments to demonstrate its feasibility. Specific contents are as follows:(1) In this paper, a partial least squares+BP neural network data analysis model is established to predict whether the hydraulic fracture can communicate natural fracture network. The results show that under the given pressure in the target reservoir hydraulic fracture turning into natural fracture is the main mechanism, which is conducive to form a complicated fracture network.(2) The paper studies the formation and preserving mechanism of acid-etched fracture conductivity to evaluate whether the fracture network has a certain conductivity. A unified evaluation method is founded on the base of the established mechanism. The results show that under closure stress of30MPa, the target reservoir fracture conductivity can reach as high as1.50Dcm, meeting the requirement of conductivity in volume acid fracturing.(3) In order to improve the modification of reservoir vertically, this paper optimizes the degradable fiber diversion technique. Based on the result of experiment of fiber plugging ability, the practical suggestions are put forward. The result of research shows that the degradable fiber diversion technique can significantly enhance the effect of volume acid fracturing stimulation.(4) On the basis of simulations and laboratory experiments, the paper improves technical ideas of volume acid fracturing and gives specific implementation process; Selecting typical well, we carried out on-site verification for volume acid fracturing Comprehensive analysis of the above research shows the volume acid fracturing technology can not only effectively increase the discharge area in landscape and the improvements in vertical, but also can remove the damage in reservoir at the same time. The technology has strong adaptability in tight sandstone reservoir that natural fractures developed, which contains certain fillings (calcium or drilling fluid). The study provides a new technology for the efficient development of the reservoir.