A New Engineering Approach for Gas Anchor Applications for Extra Heavy Crude Oil–Study Case at PetroPiar in the Orinoco Belt

摘要

Wells with high gas/oil ratio(GOR)using progressing cavity pumping(PCP)or rod pumping(RP) typically have a high gas/liquid ratio at the pump intake.For those wells,the use of a downhole gas separator is crucially important to remove as much free gas as possible from the stream reaching the pump. This makes possible to increase pumping volumetric efficiency under reasonable speed conditions and thereby improve well productivity. In applications of PCP is well known that pump performance degradation occurs when handling high fractions of free gas(GVF).Gas blockage,lack of lubricity,reduced heat dissipation,elastomeric swelling,etc.,are some of the different problems that occur to the pump before it tear down. Typically the design of downhole gas separator for light or medium crude oil uses separation efficiency values based on empirical trials and settling velocity criteria in biphasic streams.This approach has enabled the industry to mainly develop concentric configurations based on vertical positioning. In the Huyapari field,at least 43%of the wells have free gas at bottomhole conditions in the range of 70–90%.This represents a great opportunity to develop reliable gas separation technologies,looking to improve pump efficiency and run life. This article describes a pilot-scale study of two high GOR wells to evaluate the performance of a“cross flow”downhole gas separator designed for heavy oil production in horizontal wells.This low cost equipment has no moving parts;its configuration is robust,easy to build and simple to be ran in the bottomhole assembly(BHA)at slanted positions. Free gas and liquid separation theory is briefly reviewed to show the most adverse conditions for gas separation present in extraheavy crude oil at field conditions. Production results before and after application showed an increase in the annulus gas rate from 48% up to a range between 55 and 75%.This has promoted improvement in pump efficiency,greater differential pressure in the tubing column and a production increase in the well operating at a lower PCP speed.