Huge oil reserves are located in low-permeability reservoirs in the Ordos basin in China. These reservoirs have three key characteristics: low reservoir quality (10 to 13% in porosity), low reservoir permeability (0.3 to 2.0 md), and low reservoir pressures (pressure gradients of 0.0075 to 0.009 MPa/m). Fracture stimulation is essential for commercial production in these reservoirs. To better understand fracture growth behavior and to optimize treatment designs, microseismic monitoring and fracture modeling were performed for pilot wells in key areas. In some low-permeability oil reservoirs in the basin, fracture closure stress sometimes could not be obtained from commonly used pump-in/shut-in tests because pressure decline is extremely slow. Closure stress is one of the important parameters for fracture modeling. To obtain closure stress in these reservoirs, conventional pump-in/flow-back (PIFB) tests were modified and employed. Once the closure stress in the payzone was determined, the closure stresses in adjacent and/or bounding layers were estimated from sonic log and lithology data. Fracture modeling analysis was then conducted using a calibrated fracture model, which must match both the observed net fracture pressures and the fracture dimensions from microseismic mapping. This approach led to significant improvements in fracture treatment designs in these tight-oil reservoirs. The first improvement was to maximize effective fracture lengths in fracture designs. A novel staging technique was also developed to stimulate large pay intervals using a stress diversion technique without mechanical isolation. Larger treatments using a hybrid fracturing technique were recently implemented to stimulate ultralow-permeability oil reservoirs. Production results using the new stimulation techniques were significantly better than traditional techniques in the region. This paper discusses how an integrated, engineered approach was applied to stimulate tight-oil reservoirs in the Ordos basin and demonstrates the benefits of an integrated approach to developing marginal, unconventional liquid hydrocarbon reservoirs.
With the gradual deepening of Changqing Oilfield horizontal wells, horizontal wells see water phenomenon is gradually increasing, more than 80% of the current water level of high water wells horizontal wells accounted for 25.5% of the total number of open wells. High water level of wells governance means there are horizontal wells to find the mechanical plugging wells, corresponding water depth profile control, bi-directional oil wells plugging technology, by contrast, the current techniques of horizontal wells in Changqing Oilfield high water governance best suited for the corresponding injection wells be deep profile. By reason of the horizontal well see the water, see water type analysis, and ultimately optimize the construction program, citing CDST-01 blocking agent system and application of multi-level multi-round profile control technology to achieve effective governance of the high water level of wells. Field test seven wells, increasing the average single-well oil 4.5t, average moisture content decreased 68%, cumulative oil 3825t, cumulative precipitation 4585m3, a significant treatment effect, provide a reference for the next step Changqing Oilfield high water level governance and reference wells .
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