The Optimization And Numerical Simulation Study On Advanced Water Injection For Fuvang Low Permeability Reservoir

Reservoir Fuyang belongs to low-porosity and low-permeability reservoir, if development relied solely on the natural energy, after the development, pressure dropes fast, the oil production declines and pressure recovery is very difficult, and therefore must consider using advanced water injection for maintaining pressure to enhance the oil recovery. In this paper, studied reservoir Fuyang, used laboratory experiments, reservoir engineering, numerical simulation and field testing to determine network parameters of wells, the best optimal development time, reasonable injection speed, the optimal time of advanced water injection, injection-production ratio and other technical parameters. Analyzed the different pressure distribution, the chaning of pressure under different injection-production ratio and relationship between pressure propagation velocity and propagation distance, deduced stable and non-stable production capacity and pressure distribution formula, considering elastic-plastic reservoir characteristics, starting pressure gradient. Studied the effect of advanced water injection, calculated the effective utilization conditions. The main achievements include the following aspects:(1) Through physical simulation for advanced injection water using long core with several pressure measurement points.It known that, advanced water injection development is superior to hysteresis water-flooding and simultaneous water-flooding. The best optimal time for using advanced injection water is when the pressure leading edge position relative distance had reached about 39.8%, and the reasonable injection rate is to be the average speed of 39.8%. The reasonable level of maintaining pressure is 110%-118%.(2) Used reservoir engineering methods, deduced stable and non-stable production capacity and pressure distribution formula for ultra-low permeability reservoir in consideration of elastic-plastic reservoir characteristics; deduced stable and non-stable production capacity and pressure distribution formula for ultra-low permeability reservoir in consideration of starting pressure gradient; deduced stable and non-stable production capacity and pressure distribution formula considering together elastic-plastic reservoir characteristics and starting pressure gradient. While comparing the stable pressure distribution curves under three situations and the changing characteristics of non-steady pressure distribution curve characteristics over time.(3) Considering small grid spacing (20x20), used software Petrel to accurately establish the micro-structural block. Established artificial fracture model to simulate the effect of artificial fracture on the entire process of numerical simulation. In considering permeability reservoir characteristics, such as low starting pressure, basing on nonlinear numerical simulation software to do history matching and prediction, history matching of the region is very well. Simulated 10years development indicators, showed that,10 years cumulative oil production is 4.75 × 104 tons; the degree of recovery is 11%; comprehensive water cut is 71.79%; When water cut is 96%, the degree of recovery is 20.54% (50 years). For reservoir Fuyang, reasonable injection-production ratio is 1.4, and reasonable time of advanced water injection is before 3 months, cumulative water injection is 0.0052PV, level of maintaining pressure is reaching 120.13%.(4) Applied theoretical calculation and actual data of reservoir Fuyang, Economical Limit distance between the wells, technical limit distance between the wells, lmit distance between rows and rows and other effective utilization conditions.Calculated that, when oil price is changing between between 40$/bbl and 100$/bbl, economical Limit distance between the wells is between 166m and 97m. When pressure difference is changing between lOMpa and 40Mpa, technical limit distance between the wells is between 53m and 211m, lmit distance between rows and rows is 125m.(5) Combined with testing situation in using advanced water injection in the reservoir Fuyang, analyzed the initial production capacity, changes of water, effective characteristic and variation of development indicators. According to the field testing situation, reservoir Fuyang is Suitable for advanced water injection, and development effect is better than other.