Research On Theory And Key Technique Of Circulating Wash Without Discharge In Water Injection Wells

Injection well wash is an important method to clear aggregate in wellbore, reduce pollution near the perforated parts in reservoir, maintain water absorption capacity of reservoir, and improve the effectiveness of water injection. It is of great economic value and social benefit for studying the theory and technology on reinjecting the oily waste water of the produced blocks directly back into the producing formation after effective disposals.At the beginning, the history and the development of well wash and oily waste water disposal technologies in the Oilfield were presented. Through analysis and summarization of the technologies mentioned above, the main contents and basic methods for studying theory and key technology of circulating wash without discharge in water injection wells were given.According to the principles of the circulating wash technology in a water injection well, the vehicular technology of circulating wash without discharge in a water injection well was put forward. Based on Hazen's "Shallow Pool Theory" and "Theory of Stokes", a vehicular system of circulating wash for water injection wells, which was mainly composed of partition plate oil-water separator, sedimentation and separation device, trickle dosing device, fine filtering device, circulating pump, chassis, etc, was designed and the analysis of its working principle was given.The theory of oil-water separation in circulating wash was studied. A simulation model on the oil removal rate of multilayer oil-water separator was established and formulae of critical flow velocity and critical granul diametre of partition plate oil-water separator were deduced, which provided theoretical basis for CFD analysis on oil removal efficiency of flowback fluid partition plate oil-water separator.Using CFD method, influence of structure and design parameters of partition plate oil-water separator on oil-water separation efficiency was studied, the calculation of which included size (length X width X thickness), amount and space interval of horizontal tabula; size, amount, space interval and dip angle of forward and backward tabella; size, amount and structure of main plate; size of short plate and size of orifice plate, the results of which provided basic data for optimization of the partition plate oil-water separator.Technology of fungi disposal in flowback wash fluid was studied. A new type of sustaining trickle dosing device was made, which put uniform and continuous dosing into effect and had functions of efficient sterilization and flocculation in flowback wash fluid, so that flowback wash fluid can be better separated and satisfy the requirement of reinjection. A fine filtering device was made, which can satisfy the requirement of water quality for reinjection and help filter mechanical impurities in flowback wash fluid and reproduce through efficient back flushing.A partition plate oil-water separator was made thereafter, which was used in field for the test of circulating wash without discharge in water injection wells. Finally, a model of reasonable configuration and dynamic optimization in regard to the injection well wash equipment was established so that high efficiency production was put into effect.