Pressure-Compensated Flow Regulation for Waterflood Projects

To fill the need for economical and efficient regulation of injection fluidin waterflood projects, a new pressure- compensating flow regulator has beendeveloped. This flow regulator provides a means of controlling injectionvolumes without the need for constant adjustments because of changes in pump orformation pressures. This paper describes the technical aspects of this methodof regulation, its surface and subsurface applications, its advantages and somecase histories. Introduction Accurate volumetric control of injected fluid has been proven necessary for efficient waterflooding. In the past, control has often been sacrificed becausethe methods available were both inefficient and costly. The commonly used method for the surface control of water injection rates isthe choke valve – flow meter method. Figure 1 shows a single-well, one-source installation employing this method; Figure 2 shows amultiple-well, one source installation. The volume injected into each well is determined by the differential pressure across the choke valve and thechoke-valve setting. Once the choke valve is adjusted to a particular flowrate, it acts as a fixed orifice. In other words, the flow rate through thechoke valve is entirely dependent on the differential pressure across it. Tomaintain a constant flow rate, the choke valve must be adjusted continuously toany fluctuations in pump or formation pressures. These adjustments must be made based on periodic meter readings. In aninstallation such as the one shown in Figure 2, control of injectionrates becomes more difficult to maintain because a pressure change at any wellwill change the line or manifold pressure and, therefore, change the injectionrates at all wells. Choke-valve adjustments made to compensate for pressurefluctuations at any well will make readjustment of all valves necessary.Accuracy of adjustments can be determined only after flow has been allowed tostabilize. This results in a period of time during which accurate control ofinjection rates is lost. Equipment breakdowns, either at individual wells or ata pump station, will require shutting down one or all wells and will also result in prolonged periods of loss of volumetric control.