Study And Application On High Pressure Jet Broken-down Technology Using Foam Fluid

During the exploitation of oil field plugging is easily resulted from variouspollution. General technology of sand washing and broken down is not applicable tolow pressure wells because the fluid is water and it can easily produce leakage in lowpressure reservoir bed thus aggravate the pollution to it. Foam is a kind ofnon-Newtonian fluid. With its fine characteristics such as low density, low filtration,high ability of sand carrying and circulating out, stability, low damage to the reservoirbed and so on, it can be used in the low pressure wells to relieve the plugging in thereservoir bed and sand prevention tools because it can avoid the leakage of fluid andthus effectively protect the hydrocarbon reservoir.Rheological property and stability of foam are studied both theoretically andexperimentally. Rheological model of foam fluid has been established and the mainfactors affecting stability of foam have also been found out. The influences ofconcentration of foaming agent, shearing rate, pressure, temperature and waste water tofoam system performance have been researched.The laminar jet of foam fluid is researched by numerical method. Velocity decayrule, apparent viscosity distribution, and influence of K and n to axial velocitydistribution of non-Newtonian fluid laminar jet has been studied. Through experimentin laboratory, performance of foam fluid jet has been researched. The results show thatwhen L/d is less than 4, axial pressure of jet holds a constant value; when L/d is largerthan 4, axial pressure of jet decreases. Radical pressure of jet decreases. Along with theincrease of pump pressure, revolving velocity of nozzle increases which is less than that of water.Velocity distribution of power-law fluid in annulus pipeline was deduced, andimpact of K, n and size of annulus pipeline to velocity distribution and flux wasresearched.Combined with the factual material the flow law of foam in well bore and annulusis analyzed and the ability of foam to carry sand has been figured out. Numericalsimulation for sand carrying capability of foam fluid was conducted using discretephase model. The relations of sand carrying rate and residence time in foam fluid toinclination angle of annular pipe were researched. The simulation results of foam fluidwere compared with the results of water on the same condition, and qualitative analyseswere provided. It can be seen that sanding carrying capability of foam fluid is muchbetter, and it is especially suitable for well cleanout of horizontal well.Based on the above study a program of foam jet broken down has beenprogrammed which can provide the required construction parameters for the fieldthereby supervise the field application. Field application indicates that the technology offoam jet broken down can really solve the plugging problem in low pressure wells so ithas certain economic significance.