Thermo-Chemical Solution for Removal of Organic Solids Build-Up in-and-around Wellbore, Production Tubing & Surface Facilities

Abstract

ABSTRACT During production of crude oil, temperature and pressure of the produced fluid decreases along its production pathway. The reduction in pressure and temperature disturbs the equilibrium of the composition of the oil particularly the heavier components leading to their separation, precipitation and deposition at in-and-around well bore (skin effect) and production tubing. Such a deposition can choke the flow passage from reservoir to well bore and reduce the production of oil appreciably (Diagram 1). A unique two pack chemical system had been developed as an effective tool for:Removal of organic deposits, such as in-and around well bore (skin) and production tubingEnhancement of production rate The two pack chemical system when injected into the well bore through production tubing, reacts to produce in-situ heat with a reaction product. The heat generated in the system can dislodge and melt the deposits and the reaction product formed acts as dispersant and an effective surfactant. The paper presents the results on two wells which were pilot implemented in Malaysian Offshore field, Temana (TE). Among the two treated wells, one well was a closed-in well while the other was gas lift producing well. Both wells had shown appreciable decrease in skin factor, reduction in water production and sustained an additional average incremental production of 190 to 320 bpd for the past one year. Pay back period of the treatment cost was between 11 to 19 days. The wells are still producing after one year of treatment. The two pack chemicals system and related chemicals, and their reaction product are compatible with crude oil, rock formation, tubular steels and oil field rubber parts. INTRODUCTION The rate of crude oil production in a well varies directly with reservoir pressure and inversely with the resistance experienced to its flow from reservoir to storage tank. During the production process, the temperature and pressure along the production path of the producing wells decrease with the change in oil composition, increase in viscosity and change in chemical equilibrium with respect to crude oil and water produced. The change in equilibrium can lead to separation, precipitation and deposition of heavy organic components of the crude oil and inorganic scales from the formation water. While nature and extent of the organic solids depend on the composition of crude oil, the nature and extent of the inorganic solids depend on the composition of formation water. As the change in temperature and pressure is more apparent at in-and-around the well bore (Diagram 2); maximum deposits of heaviest solids can be expected at this location. Such deposits can choke the formation in-and-around well bore reducing its effective permeability appreciably and reduce the rate of crude oil production. Not only solids deposit at in-and-around well bore, but production tubing and flow lines as well (Diagram 3). The presence of fines (sand, silt, clay and scales) at in-and-around well bore and production tubing can further deteriorate the flow passage chocking thereby further reduce the crude production. There are two types of organic deposits. One is composed primarily of paraffin (commonly refers as wax) and the other of asphaltene.