Chemical Control Techniques for the Paraffin and Asphaltene Deposition

Abstract

Abstract Paraffin related problem appears through out the production process of nearly all kinds of crude oils all over the world. It also appears in the dewatering process and the long distance crude oil transportation. In Daqin Oil Field in northeastern China, 150 million RMB is spent on the cleaning up the paraffin deposition (including the total expense on cleaning up the paraffin deposition on various surfaces of production equipments by the mechanical, thermal, chemical etc. methods). Just as the same, asphaltene deposition problem is also encountered in the oil production process. This paper focus on the discussion of paraffin deposition and its chemical control technique. The paper introduce the latest research and development of chemical additives (DQ, KOW, AOA, ZHJ) for the control of paraffin and asphaltene and their successful application on 2000 wells in Chinese oil fields. In the oil field application, chemicals were added into the oil tube or annular space, or squeezed into the oil formation so that the deposition of paraffin and asphaltene was inhibited. Oil wells treated with DQ, KOW, AOA, ZHJ were all kept on long time normal production, the times of repairing equipment and shutting up oil wells were greatly reduced. Also the productivity was enhanced and the production cost was decreased. Annual economic benefit by using of this chemicals was about 21, million RMB. The design of paraffin inhibitors in the paper was based on the theory of co-crystallization, the theory of surface chemistry and colloidal dispersion chemistry. DQ, KOW, AOA were thus designed and have satisfactory properties. The paper also discuss the mechanism of paraffin deposition inhibition. Introduction There are many literatures[1–13] reporting paraffin problem. They can be divided into two kinds. The first kind is mainly related to the research of mechanism of paraffin deposition and the set up of physical and mathematic models and also the development of the softwares for analysis and anticipation of paraffin deposition potentiality for a target oil field; the second kind is specially concerned with a practical way of resolving paraffin deposition problem, such as mechanical, thermal, chemical, physical etc. methods. This paper mainly describes specific property of a few chemical paraffin inhibitors and an asphaltene inhibitor and their application in many Chinese oil fields. Paraffin deposition generally consists of wax, asphaltene, resin and sands etc. The main component is wax. Wax is solid state normal alkane with 15~80 carbon atoms and very few branch chain or even no branch chain. Under the oil formation conditions, the wax resolved in crude oil. But in the course of crude oil flowing through oil formation into the bottom hole of the well and then flowing up to the ground, because of the decrease of pressure, temperature and the out come of gas, the wax is separated out to form crystals. The wax crystals will grow, aggregate and then precipitate on the wall of oil tube. The process of wax precipitation include three stages, that is the wax separation, the growing up of wax crystals and the deposition of wax. If the wax crystals are separated from the active points of some solid surface (such as the metal surface, the sand surface) and continuously grow up, there are only two stages for the paraffin deposition. Control of any one of the three stages of wax deposition will reach the goal of paraffin inhibition. Commonly used electric heating cable is a example of control wax deposition at the first stage (wax separation) while the glass oil tube and coating oil tube are the examples of control wax deposition at the third stage (wax deposition). The introduced application of DQ, KOW and AOA paraffin inhibitors are the examples of control wax deposition at the crystal growing up and wax deposition stages.