A Field Experience Against Corrosion: Performance Report of Bronze

Abstract

This work describes the experience in the use of Bronze-Aluminum coated sucker rods at Chihuidos de la Sierra Negra and Lomitas fields, operated by REPSOL-YPF (Rincón de los Sauces - Neuquén). This new material was developed specifically to work in the corrosive environment of the oil producing wells of those fields. This development was a result of a team work, manufacturer and user. Its objective was to find an acceptable solution (technical and economics) for the sucker rods used at these fields. Introduction Chihuidos de la Sierra Negra and Lomitas fields are located at in Neuquén province, Argentina. Those fields started their development since the end of 80's. Producing formations are Troncoso and Avilés (1000–1100 and 1300–1500 m. deep) with 5.5 OD casing and 2 7/8" OD production tubing. Starting 1997 those fields had 652 producing wells (Gross production rate of 40000 m3/d, 20000 m3/d of oil production rate). In 1993 started the secondary recovery program (selective water injection). This program started by injection of 500 m3/d, today the rate of injection is about 82000 m3/d. As a result of that, water cut has growth from 10% to 50–70%. GOR of the wells are 10/20, with a 60% of CO2 in the gas. Initially those fields were lifted by sucker rod pumping, using API 86 or API 76 rod strings. As those fields were responding to the secondary recovery program, dynamics levels were growing constantly. So the operating company decided to adequate the lifting systems:Electric submersible pumps were installed (high production rate wells)Re-desing of beam pumping installations First stage involved the use of high strength sucker rods (3–4 wells). Due to the severity of corrosive environment (not recommended for high strength rods) and the problems with the corrosion inhibitors, those rods were pulled out from these wells. The operating company decide to start a program of corrosion inhibition, in this way they increase the performance of sucker rods. Despite of that, certain conditions as wearing, high velocity flow rates, high fatigue loads result in a necessity of a new material for certain wells. In these wells Grade D rods were not applicable, in fact there were wells in which rods had a service life less than 60 days. Development 1 - Wells characteristics Typical installation of beam pumping wellsDepth: 1.400/1.800 mTubing: 27/8"Pump bore size: 2.75"Pumping Unit:: C-912–365–192Stroke: 168"-192"Pumping speed: 8/10 spmProduction Rate: 100/200 m3/day (50/70% Water cut - GOR 10/20)String type (before coated rods): API 87 1–2 Corrosive environment1–2–1 Chemical data from water (producing wells)Density (gr/lt) 1,0 - 1,10Temperature (°C) 40/50pH (well head measurement) 6,00/6,50