Well Pattern Optimization In Waterflooding Exploitation Of Heavy Oil Reservoir Within Sheet Sand

Front sheet sand in delta is widely distributed in large area, which is contiguous grow in the lateral direction, the vertical lenticular sand body, usually between 1 to 5 m, with a sand from fine to coarse anti rhythm in the vertical or homogeneous rhythm.Sheet sand is fine sorted and rounded, with a stable distribution in flat. Reservoir within sheet sand has a high quantity of oil and gas charging, however, the sand body is very thin, makes it lack of development experience.Heavy oil reservoir has a characteristic of high viscosity, high content of wax, and poor mobility. To exploit heavy oil, the main idea is to reduce the viscosity, reduce flow resistance and increase the reservoir drainage area. For heavy oil in thin-bedded sheet sand, water flooding recovery is the most essential development methods.The current study of water-flooding in heavy oil reservoir within sheet sand is very poor, no development model can be adopted. In order to find out the most efficient way of water-flooding in heavy oil reservoir within sheet sand, Mian 22 S3S3 reservoir in Bamianhe oilfield is typically selected to do simulation study.Based On full study of sheet sand and the seismic, drilling, geological, laboratory analysis and other information of Mian 22 S3S3 reservoir, a 3D model of Mian 22 S3S3 reservoir was built using 3D geological modeling software calling PETREL.The 3D model including facies, water saturation, porosity and permeability properties. After fitting with verified reserves, the model can be considered correct.Simulation model of Mian 22 S3S3 reservoir was built in ECLIPSE numerical simulation software, combine with the geological model and the fluid PVT properties. Calculating 11 production wells production data in ECLIPSE black oil model can obtain dynamic Mian 22 S3S3 reservoir Situation. History matching with the calculated data and the actual production data can modify the simulation model further.After history matching, a suitable region was selected to demonstrate the size of the vertical and horizontal well network, horizontal well structure in heavy oil reservoir and injection-production ratio, etc.In order to get the best parameters, providing critical data for the development of heavy oil reservoir within sheet sand. The parameters are below:(1)For Vertical well pattern, staggered well pattern and inverted rectangular nine-spot well pattern are selected. When optimizing space between wells in staggered well pattern, rows were equaled to 200m,140× 200m,160×200m,180×200m,200 × 200m,220×200m patterns were designed, when optimizing rows, space between wells were equaled to 180m,180×140m、180×160m、180×180m、180×200m、180×220m patterns were designed. Simulation results show that the optimum space between wells is 180m and the rows is 160m. when optimizing space between wells in inverted rectangular nine-spot well pattern, rows were equaled to 200m,160×200m、180×200m、 200×200m、220×200m、240×200m patterns were designed, when optimizing rows, space between wells were equaled to 220m,220×160m、220×180m、220×200m、 220×、220×240m patterns were designed. Simulation results show that the optimum space between wells is 220m and the rows is 200m.(2) Horizontal well structure design in heavy oil reservoir, length and flat position are the main point. An ideal model was used when simulation. When optimizing horizontal well length,100 to 800 meters are simulated, when optimizing flat position, 60-120 meters away from the edge of the water are simulated. Simulation results show that the best length is 200m and the best flat position is 100m away from the edge of the water.(3) For horizontal well pattern, vertical injection wells and horizontal production wells rectangular five-spot well pattern is selected. When optimizing space between wells in staggered well pattern, rows were equaled tol60m,180×160m、200×160m、 220×160m、240×160m、260×160m patterns were designed, when optimizing rows, space between wells were equaled to 220×120m、220×140m、220×160m、220×180m、 220x200mpatterns were designed. Simulation results show that the optimum space between wells is 220m and the rows is 160m.(4) For injection-production ratio optimization, V injection/V recovery= 0.7,0.8, 0.9,1.0,1.1 are simulated in all optimal well patterns. Simulation results show that the optimum injection-production ratio is 0.8.(5) Comparing all optimal well patterns in the same injection-production ratio,the best well pattern is vertical injection wells and horizontal production wells rectangular five-spot well pattern, with the best space between wells 220m and the rows 160m.After the simulation of Mian 22 S3S3 heavy oil reservoir within sheet sand, an ideal heavy oil reservoir within sheet sandc was built. Simulation results show that the best well pattern is vertical injection wells and horizontal production wells rectangular five-spot well pattern, with the best space between wells 220m and the rows 160m.The result is the same with Mian 22 S3S3 heavy oil reservoir within sheet sand, two result supported each other and shows the reliability of the results.