Zhongyuan Oilfield Continuous Gas Lift Wells To The Uninstall Process Simulation

At home, Wendong Oilfield is the first base of gas lift in large scale. We all know gas lift unloading is the key link of production. Unfortunately, in practice, we lack of the methods to anticipate and control it well, consequently, it often appears that the failure of unloading leads to the low lift efficiency, even having to pull out the tubing string to adjust the valve spacing. By the simulating, engineers can anticipate the behaviors of production before the gas lift strings are put into the borehole. Which have the important significant on improving the efficiency of system and reducing the operation cost.On the basis of the study on the gas lift unloading process, the paper presents the unloading comprehensive mathematical model which is based on the theory of mass and momentum conservation, and develops the simulating software. In addition, the field test demonstrates the reliability of the results. The main contents and conclusions are as follows:1) Gas lift unloading is a complicated process, covering flow patter and process change. It is the difficulty of gas lift technology. By the simulating, the study determines the relationships between bottom hole flowing pressure, liquid level in the tubing and annular, annular wellhead pressure, gas injection through the surface choke, upstream and downstream pressures, on off states of the valves, liquid and gas rates through the valves, etc. and time.2) In terms of whether gas entering into the production string or not, unloading processes are divided separately into gas-liquid two phase transient flow, single phase unstable flow. Afterwards, mathematical models are developed separately. Finite differencing is adopted to solve the above the mathematical equations depicting the unloading process, and simulator is programmed.3) In the purpose of improving the efficiency of gas lift system, it is studied well for the continue gas lift unloading in theory, and the reliabilities of results are validated through the practices.Lasting two-year theoretical and experimental investigation, the penman thinks the main innovations are follows:1) At home, it is the first time to carry on the simulation of continuous gas lift unloading in system. The paper presented the numerical model of unloading process. With the simulating software, engineers can simulate the unloading process, consequently, it is also easy to reduce the blunders, to overcome the failures, and to enhance gas lift efficiency.2) The core parts which are used to test dynamically the gas lift unloading process are designed and manufactured, including the continuous gas lift launching pressure gauge device which can use in practice. It has been authorized China patent of utility (patent code: 200420010498).