| Daqing Oilfield development process shows that with the further recovery of Daqing Oilfield and the engineering and geological factors,the casing of oil and water wells will inevitably appear damage of different degree. Due to the little distance between the internal reservoir and N2 section in Changyuan Oilfield, there are some problems such as long-term production, cementing quality and the fault that leads to the N2 section casing damage of oil and water wells.Now there are some complex casing damage areas like La 7-30 and west area of the Southern district. In view of the serious situation of casing damage,the number of casing retrieving increases year by year,and it’s the only workover technology that can reconstruct the structure of oil and water wells.But in the process of casing retrieving,in the course of milling at the large section of shale formation,the work-over fluid viscosity and shearing force increase rapidly,and in the course of milling-reaming and dilling-plug, it’s appeared that the cement contamination is aggravating, the work-over fluid viscosity and shearing force increase faster.It needs to allocate or replace work-over in the case of serious fluid calcium contamination.These problems ultimately lead to the work-over loss and extend the construction period. On the base of the investigation and analysis of the engineering geological characteristics of casing retrieving,it carried out a lot of experiments in lab and rationally deployed work-over fluid drug to research the anti-calcium work-over fluid system of casing-retrieving.The research shows that the new work-over fluid system has a significantly improve on the ability of inhibition of coating,anti-calcium contamination, filtration and anti-pollution, etc.It can solve the problem of the work-over fluid calcium contamination,sidewall instability and resistance, reduces complications and accidents, and ultimately offers a vary good technological ensure of casing retrieving of Daqing oil- field. |
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