ABSTRACT
To solve the problem of discontinuous data obtained by concentric bridge layered injection technology due to its artificial controlled mechanical water distribution pattern, Changqing Oilfield has done enormous work on intelligent layered injection. At present, two technologies have been developed, which are intelligent layered injection technologies with cable and without cable. However, they are faced with two major difficulties of downhole communication and flow rate measurement. In this paper, based on throttling equation and remote wireless communication via pressure wave, that is widely used in Measurement while Drilling (MWD), a downhole automatic water distribution technology is proposed. By means of pressure wave signals transmitting in wellbore, the surface control system sends water regulation orders to intelligent regulator and receives injection data from it. Based on pressure difference before and after water nozzle, a flow rate measurement without flowmeter is developed. In last two years, this new technology has been applied in 138 water injectors in Chanqing Oilfield and proved to be effective. Field application demonstrated that the downhole remote wireless communication via pressure wave could realize real-time supervision of single layer pressure and flow rate, and the wireless communication distance reached to 2879m. According to analysis results of historical flow rate data, the qualified rate of single layer flow rate was maintained above 90% in long term. By successful application of this technology, waterflooding efficiency of the pilot area was improved remarkably. The average water absorbing thickness was increased from 19.3m to 20.4m, and the water drive reserves producing degree was increased from 65.2% to 67.7%. Meanwhile, the natural decline rate was decreased from 5.8% to 2.1%, and the water cut increasing rate maintained the same at 1.3%. This proposed technology provides an effective way of real-time monitor and downhole automatic control for layered waterflooding in low permeability reservoir. The real-time data obtained from it are meaningful in waterflooding performance evaluation and development optimization.
