Asphaltene deposition causes serious problems in production operations, from the reservoir, through production tubing, and in surface facilities. This work presents a systematic approach, preventive and corrective, taken at Intevep S.A to handle asphaltenes deposition problems at the different stages of crude oil production A predictive tool has been developed at Intevep. It is a software based on thermodynamically considerations, SPLASH (Solid Phase fLASH). It requires as input data, PVT and dead oil characterization and delivers the phase diagram of the crude oil. Phase diagrams obtained are shown. If as a result of the simulation, asphaltenes deposition is expected, preventive actions are recommended. We have successfully used continuous down whole injection of dispersants. As in the case of surface facilities, dispersants are specifically selected for each crude. Additional production in 1995 was estimated in 900000 barrels. A reservoir simulator has been developed as well. This is an in-house modification of a compositional commercially available simulator. It allows to simulate the behavior of the reservoir under asphaltene precipitation conditions. A simulation example for a reservoir in easternVenezuela is presented.
Asphaltene deposition causes serious problems in production operations, from the reservoir, through production tubing, and in surface facilities. This situation takes place worldwide. The problem has been widely reported. A recent review in this area was published by Kokal and Sayegh. This paper reviews a systematic approach to deal with asphaltene precipitation in the well bore, surface facilities and the reservoir, developed by a multidisciplinary team at Intevep S.A.
As crude oil is produced, it can undergo phase changes as a result of the different pressures and temperatures. Normally, under reservoir conditions the crude oil is a single phase liquid. As it is produced through the well bore, pressure and temperature decrease and depending on the crude composition a gas and solid phase may appear. This is illustrated in Fig. 1. It can be seen in the figure that the solubility is minimal around the bubble point. Other reasons why asphaltene deposition may occur are mixing of crude with light oils or gases used in miscible flooding, that could lead to asphaltene precipitation. Acid stimulations can equally cause organic depositions. The appearance of the solid phase may lead to plugging of the production tubing or formation, with the obvious operational and economical burden.