Shiyou shiyan dizhi (Nov 2020)
Origin and significance of wellbore sediment in reservoir development: a case study of well Gaotan 1 in Junggar Basin
Abstract
During the development of oil and gas reservoirs, wellbore sediment will bring a series of problems, so it is important to identify the cause of wellbore sediment. The discovery in well Gaotan 1 is an important milestone in the history of oil and gas exploration in the Junggar Basin. However, with the exploitation of crude oil in this well, a large amount of black solid insoluble sediment blocked the wellbore. The composition of the sediment was clarified by various experimental analysis methods, such as group component analysis, gas chromatography, liquid chromatography, wax content analysis and pyrolysis experiments. The results allowed the study of the formation mechanism of the solid-phase sediment in well Gaotan 1 and the development of site control measures. The sediment in well Gaotan 1 is composed of soluble organic matter (mainly asphaltene) and silty sand (mainly fine silt). In the process of crude oil exploitation, the temperature and pressure of crude oil decrease from stratum to wellbore, and the light components in crude oil are preferentially separated and flow out, destroying the dynamic stability of the crude oil, and asphaltene dissolved in the crude oil to precipitate and flocculate, and finally to be adsorbed on the pipe wall. At the same time, silty sand at the bottom of the well is mixed with the asphalt precipitate with fluid flow, and grows with asphalt precipitate. This may be a common phenomenon in the oil and gas production process under high temperature and high pressure conditions. It is necessary to choose strong polar asphalt dispersants to increase the stability of the crude oil system, and use strong polar reagents for chemical cleaning of the scaled wellbore. More bottom hole filters are required to reduce sand and mud solid particles.
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