Diagnosis and treatment of naphthenate deposits embedded with other organics and inorganics

Abstract

Napthenate solid deposits in oil wells tend to contribute towards vital flow assurance issues and production decline due to formation damage, increase in the weight of the crude by almost 12% and restriction in the production tubing and around the wellbore. This paper showcases an operational excellence approach in diagnosis of oil producing wells, which might have the potential to form naphthenate deposits along with other inorganic scale, corrosion product and organics. In this work, deposits, crude and formation water samples from an oil field located offshore Peninsular Malaysia was used as a case study to quantify the presence of naphthenates. Various analytical tests such as modified SARA analysis, cationic and anionic analysis of formation water, Total Acid Number (TAN) analysis, pH of the crude sample and also X-Ray diffraction (XRD) on the samples were conducted in the laboratory to understand and affirm the occurrence of the naphthenates. Based on the analytical results, it was concluded that naphthenate deposit was the main issue in the well. Also, there were possibilities of wax and other inorganic deposition to take as identified by the test results. Hence a single step micro emulsion formulation was designed that can enhance the productivity of the well by injecting the formulation into the designated zones to dissolve naphthenate embedded with inorganic material, simultaneously dissolve/disperse organic deposit, break the naphthenate induced tough emulsions and change the wettability characteristics of the formation rock towards water wetting to ease the flow of oil into the wellbore. The formulation of the speciality micro-emulsion is vastly based on the characteristics of the formation fluid, nature of the sample, reservoir and operating conditions. The application of this study is a preliminary attempt to establish guidelines for early detection of problems related to naphthenate and possible chemical remedial, thereby, stimulating preventive measures and attenuation plan which can be formulated and replicated in wells with naphthenate problems in various parts of the world.