Improving Run Life in PCP Wells with CO2 and H2S Concentrations Using Tungsten-Alloy-Coated Rods and Couplings

Abstract

The company Petrogas E&P was established in 1999 by acquiring onshore block 7 in Oman. Over 23 years, Petrogas E&P has continuously grown by acquiring several blocks in Oman, India, Mozambique, Egypt, Netherlands, Germany, Denmark and in the United Kingdom. The main operations are in Oman, Netherlands and in the UK. Since 2007, Petrogas is the operator of Rima Cluster small fields in southern Oman. Artificial lift, mainly rod driven Progressive Cavity Pumps (PCPs) and Beam Pumps (BPs), is required to produce oil with an average specific gravity of 21 °API to surface. Parted rods are the main reasons of well failures and rods present the weakest part of the completion. Some of the wells in Petrogas Rima show high angles of inclination, complex trajectories and certain levels of hydrogen sulfide (H2S) & carbon dioxide (CO2). Completion failures due to parted rods lead to production deferment and workover interventions because of required rod string replacement. In general, sucker rods are made of a certain grade of steel and these steels are prone to corrosion in an aggressive environment due to the presence of carbon dioxide and sulfide in the crude oil. A coating solution for sucker rods and couplings was implemented to reduce the influence of corrosive environment in some wells. The lower coefficient of friction resulting from the coating reduces the abrasion between the coupling and the tubing. In that way, the risk of tubing holes can be reduced. After a coating solution was implemented in selected problematic wells, the rod run life could in average been tripled with no failures observed as of this writing.