The gas control and oil production technology based on gravity drive of nitrogen injection in the Yanling buried-hill oil reservoir

A secondary gas cap is formed at the top of the Yanling buried-hill oil reservoir of the Huabei Oilfield after nitrogen injection is carried out. Under the action of gas drive and gravity segregation, two fluid contacts (gas/oil contact and oil/water contact) and three fluid distribution zones (artificial gas cap, oil enriched zone and water flooded zone) are formed. Gas, oil and water coexist in the wellbores of the response wells at the top. In order to ensure the normal production of the oil wells, the oil production technology of liner hanging is tested in the original wells with permanent packer, but the test result is worse. In this paper, the characteristics and problems of the earlier oil production technology of nitrogen injection were discussed from the aspects of practical production and theoretical analysis. It is indicated that the simultaneous production of gas and liquid is inevitable in the middle and late stages of oil well production. Nitrogen can hardly mix with the crude oil, so once it flows into the wellbore, it will occupy the liquid flow channels quickly. As a result, the oil well produces only gas, but no liquid, potential safety hazards exit due to the high-pressure production at wellhead, casing and oil transportation pipeline, and all the oil wells at the top are shut down unexpectedly. In order to solve the problems of oil well production under the condition of immiscible vertical pipe flow, the dual-tubing gas control and oil production technology was adopted according to the pressure equilibrium principle of U-shape tubing, and its pipe string was optimized. In this way, the gas and liquid shunting and the gas control and oil production are realized.