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

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractConventional sucker rods (working under torsion loads) are used nowadays to drive PCP pumping systems (Progressing Cavity Pumps). Conventional rods have been developed to work under alternating tensile stress, not under torsion stress. The use of these rods to drive PCP systems has several limitations and problems.These limitations result in high operative costs for artificial lift systems. Also, in many cases the high capacity pumps commonly used today cannot be driven, because of their high torque requirements.

The present paper has for purpose to describe the experience with the use of AISI 4320 steel sucker rods in the corrosive environments of Unidad Económica Rincón de los Sauces (Neuquén -Argentina) of Repsol-YPF and show the results obtained until now.

The Cerro Drag?n oilfield, operated by Pan American Energy, has producing oil wells that use rod pumping systems with average depths of 2,440 m (8,000 ft) and fluid rates as high as 200 m3/d (1,300 bfpd). In this oilfield, the pulling operations exhibited a high incidence of pin breaks, generally located in the 22.23 mm (7/8 in) OD taper that we concluded to be the weakest part of the entire string, as we will show. In order to solve this problem, a new sucker rods design was developed by creating a new non- API 22.23 mm (7/8 in) sucker rod with ends of 25.4 mm (1 in) in order to reinforce the string. This technical work describes the development of this technology, as well as the experience in the field, with excellent results p to the present. Introduction erro Drag?n is an oilfield located in the Golfo San Jorge Basin (see Figure 1). This field has 1,800 oil producing wells, with 1,642 wells lifted by rod pumping systems. Average pump depths are 2,440 m (8,000 ft) with oil producing rates as high as 200 m3/d (1,300 bfpd). In 1988, a secondary recovery project was started. The water injection rate was raised (Figure 2), resulting in higher production rates and consequently higher loads to all of the components (rods, pumping units, etc.) of the lift system. Associated with this increase in the production rates, an increase in failure rates was observed. It was determined that the main cause of this failure rates increase was connection failures; in particular, the 22.23 mm (7/8 in) pin failures. Approximately 18% of the failures were caused by 22.23 mm (7/8 in) pin breaks. As a result, a team was established between the rod supplier and the operating company to work together to improve the fatigue resistance of the 22.23 mm (7/8 in) connection. The result of this teamwork was a new non-API sucker rod with a 22.23 mm (7/8 in) diameter and a threaded connection of 25.4 mm (1 in). Currently, there are 60 rod strings installed, the oldest ones with an operating service life of about four years, and there has been just one failure (the oldest one failed after 1,499 days in service). The installation of the improved sucker rods in 160 wells (thosewith the higher failure rates) will result in savings of almost US$2 MM/year. This paper describes the development of the rods, as well as the experience in the field. Failures History Due to the increase in the IPA (index of interventions per well per year) for wells lifted by rod pumping (Figure 3), work was conducted to understand the different causes of the failures. The first conclusion was that the sucker rod failures were growing at a constant rate, corresponding to the increment in the production rates.

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