Theory And Application On The Multi-layer Water Injection

Oil-field waterflooding is the main producing method on onshore oilfield at present.It can complement layer energy efficiently,it is important for improving oilfield recovery and ensuring oilfield high and stable production.But because of layer's anisotropy,it is low efficiency if we inject water to layer.The layer should be divided rationally to inject water into each layer and the rate of flow should following the request.The rule of flow should be researched fluid flow was allocated in well at the process of fluid flow was allocated in well when water was inject into layer.This article divides the fluid flow in well into three parts,which are the pipe flow in the well bore,throttle flow in the water distributor and the seepage in the reservoir.In the study of throttle flow,the relationship between the wellhead pressure and the wellbore pressures of the layers is built up through the Bernoulli equation.In the study of throttle flow,the flow in the water distributor is simulated by numerical methods and it is found that the total pressure loss is proportional to the square of the flow rate into the water distributor.In the study of the seepage in the reservoir,the wellbore pressure formulas of the vertical well and the vertically fractured well are derived with infinite boundary and constant flow conditions.Considering all thethree types flows,the relationship between wellhead pressure and tap diameters of water distributors of different layers is proposed.Finally an effective method named pressure rise method is given to adjust flow rates of the layers.When changing the wellhead pressure,flow rates and pressures of the layers can be measured.On the basis of the measurement the water injection indexes are calculated.Then proper wellhead pressure and tap diameters will be calculated through water injection indexes and flow rates of the layer,the wellhead pressure should be as small as possible when the flow rate error limits are satisfied in order to reduce the costs.In order to improve the efficiency of water distribution and reduce the work of operator,a series of experiments was conducted in the lab.Through the unsteady flow equation of motion in wellbore was built,the wellbore pressure distribution rule was establed.The experiment of local resistance coefficient of nozzle and the rule of flow coefficient was conducted when the testing apparatus had been built to establish the loss curve of nozzle pressure.The software of water distribution was made to improve the efficiency of water distribution and set up a reasonable system of injecting water.