Organic Deposition: From Detection and Laboratory Analysis to Treatment and Removal

摘要

Organic deposition predominantly in the near well bore and in production tubing can create serious oilfield problems such as flow restrictions, near wellbore damage, efficiency of crude processing units and etc. As the reservoir depleted over the time, the solid deposition can lead to a steep decline in productivity of wells. The deposition of organic solids is one of many flow assurance problems faced by operators in Malaysia. It has been observed that, after years of production, many fields in Malaysia are suffering from organic solid deposition problem. This phenomenon is predominantly caused by changes in temperature, pressure and composition/morphology of the crude oil over time. To perform organic deposit removal treatment and prevention in the well, the nature of the solid should be characterized. If the deposit sample is organic mainly, it is important to quantify the various organic fractions of the solid sample collected from the production facilities. This paper explains how SARA analysis was modified to detect not only Macro-crystalline waxes (Saturates), asphaltene, aromatics and resins but also micro-crystalline wax and naphthenates. The content of each of above component will affect the method of treatment and the chemical formulation to treat the well. By knowing the composition of the solid sample along with Crude’s Colloidal instability index (CII), Pour point and Wax Appearance Temperature (WAT), a customized chemical formulation can be designed. Lab studies were performed on solid samples collected from several wells to detect the flow assurance related issues prior to design of chemical formulation. With the analysis of the production data, history matching, and etc, a customized chemical formulation was developed to treat the wells. The proposed chemical formulation consists of 2 specially designed pills which would be simultaneously injected to the wellbore, which generates heat and ester once comingles. The heat melts the deposits while the ester disperses the melted solid. The initial studies of the treatment showed promising results; moreover the field implementation was very successful and proven significant increase in production rate. This novel system that combines both thermal and physical energy, evidenced to work effectively for wide range of organic compositions. Implementation of this system made it possible to restart the production from those wells which were idle due to extensive organic deposits. This technique was also often used to rejuvenate the old wells with low production rate. This paper discusses the diagnostic process and successful implementation of the proposed treatment in several oil wells in Malaysia.