Efficient development technology of narrow oil rim with gas cap and edge water & its practice

There is less mature experience on the development of oil rim with gas cap and edge water and its efficient development is very difficult. The narrow oil rim with gas cap and edge water in JZ Oilfield in the Bohai Sea area is faced with a series of problems during its development, e.g. well pattern optimization in the early stage of development, remaining oil potential tapping in the middle and late stages and high-difficulty management after gas channeling and water coning. To solve these problems, the well pattern optimization, oil-gas-water three-phase migration laws, remaining oil potential tapping strategies, gas channeling and water flooding characteristics and oil production stabilizing & water production controlling (gas production controlling) technologies of oil reservoir with gas cap and edge water were studied by taking the oil reservoir with large gas cap and weak edge water and that with small gas cap and strong edge water as the representatives. And according to the research results, a new model of horizontal well pattern was established. The horizontal well in the oil reservoir with large gas cap and weak edge water is vertically located at 2/3 of the vertical distance of the gas-oil contact; and that in the oil reservoir with small gas cap and strong edge water is vertically located at 1/3 of the vertical distance of the gas-oil contact. Large-scale 3D physical model and numerical simulation show that the higher the oil production rate is, the faster the oil-gas contact and the oil-water contact move towards the production well. Then, based on the cognition that the remaining oil between horizontal wells is distributed in the shape of " potato” , the interwell filling scheme was prepared. Based on the production test data of the working area, 3 gas breakthrough diagnosing charts and 2 water breakthrough diagnosing charts were set up by means of reservoir engineering method and numerical simulation method, and they play an effective role in guiding the implementation of oil production stabilizing & water production controlling (gas production controlling) measures. It is predicted from above mentioned studies that the recovery factor can be increased by 2.3% if JZ Oilfield is developed by using these technologies for 10 years with the water cut below 25.0% and gas/oil ratio below 700 m³/m³. The research results can be used as the reference for the development of similar narrow oil rims with gas cap and edge water.