SPE 149944 Succesful Application of Metal PCP Rechnology to Maximize Oil Recovery in SAGD Process R. Arystanbay, SPE, W. Bae, SPE, Huy X. Nguyen, SPE, Sejong University; S. Ryou, SPE, W. Lee, T. Jang, SPE, Korean National Oil Corporation Caspian Branch Copyright 2011, Society of Petroleum Engineers This paper was prepared for presentation at the SPE Heavy Oil Conference and Exhibition held in Kuwait City, Kuwait, 12 14 December 2011. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright. Abstract Enhanced oil recovery methods (EOR) methods such as Steam Assisted Gravity Drainage (SAGD), Cyclic Steam Stimulation (CSS), steam drive, solvent and electric heating allow production of highly viscous crude oil at elevated operating temperatures (>160 C). The choice of artificial lift technique is critical to overall well performance. Therefore it has been a challenge to find a reliable artificial lift pumping system for heavy oil thermal recovery. Available options such as beam pumps and electrical submersible pumps (ESP), which are well proven in the petroleum industry, are not particularly well suited for thermal production. Progressing Cavity Pumps (PCP), with elastomeric stator, are economic to run and have performed well in heavy oil cold production. Since their elastomers are limited in temperature (<160 C), a metal PCP technology has been developed through numerous research works to meet the high temperature requirement of SAGD and other thermal recovery processes. This paper describes the successful application of KUDU PCM Vulcain TM metal PCP systems for SAGD process in Athabasca reservoir, beginning from 2007. We made analysis on production optimization in SAGD well pairs equipped with the PCM Vulcain, which consists of a hydroformed metal stator and matching rotor utilizing special metallurgy to resist wear and maximize run life. In particular, the production with metal PCP in these wells reached the value of 200 m3/d at pump intake temperature of 200 C, performing volumetric efficiency of 82%. In general, the field results have demonstrated that the strong resistance of metal PCPs to chemical and mechanical degradation makes them a good alternative for the cold production of heavy and extra heavy oil with relatively high bottomhole temperatures and high aromatic, CO2 or H2S concentrations. This paper can be a guide for special heavy oil hot production PCP technologies to be spread and applied for EOR projects widely in the world. Introduction A huge quantity of heavy oil and bitumen resources has been discovered worldwide. According to Chen s research (2009), the proved reserves of heavy oil are estimated more than 1.8 trillion barrels in Venezuela, 1.74 trillion barrels in Alberta, Canada, and 20 to 25 billion barrels on the North Slope of Alaska. Among the estimated 170 billion barrels recoverable reserves of Canadian oil sands, 20% can be recovered by mining techniques where the reservoir depth is 90 meters or less. The remaining 80% of the resource has to be recovered in-situ (in place). The existing recovery methods involve cold/chops production or thermal activation - whether steam, such as SAGD, CSS or steam drive; electrical heating, like electro thermal dynamic stripping process (ET DSP); or combustion, such as toe-to-heel air injection (THAI); or solvent injection, mainly vapor extraction (VAPEX). Combination of those processes can be used as well, and several research projects may bring other innovative solutions in the nearest future. Key to any thermal recovery process is artificial lift, which is required due to the very high density and viscosity of crude and relatively low reservoir pressures. The main challenge with hot pumping is the rather high temperatures often required (up to 260 C for SAGD and 350 C for CSS). The dominant pumping technologies available are beam pumps, electric submersible pumps, and progressing cavity pumps. However all these pumps have their peculiar limitations for hot production. While
2 SPE 149944 beam pumps offer high temperature service, they are limited in the flowrate they can deliver. On the other hand, ESPs can handle high volumes of low viscosity fluids, but are still limited in terms of maximum operating temperature. Conventional PCPs also suffer due to the limitation in operating temperature of elastomer. Through research work conducted by PCM and Total, metal PCP technology has been developed using hydroforming technology to meet the high temperature requirements of SAGD and other thermal recovery processes. This paper describes the application of metal PCP systems for SAGD process in Athabasca reservoir. The production analysis was made in SAGD well pairs equipped with PCM Vulcain at the B field, located in Alberta, Canada (note we call the field B, since its name is confidential). The metal PC Pumps were installed to enhance and optimize production instead of the previous artificial lift systems, employed in several well pairs. Conventional and metal PCP Progressing cavity pumps, invented and patented by Rene Moineau, have found numerous applications in many industries as a means to efficient transfer, transport and/or lift fluids of a diverse nature. The use o PCPs as an artificial lift method for oil wells has gained increasing acceptance since their first commercial use in heavy oil applications in the 1980 s, and they have now become the lift method of choice in numerous oil field developments worldwide. PCPs are very simple in design and operation. The pump is composed of two basic parts: the stator and the rotor. The stator has a dual helical profile, and the rotor, rotating inside the stator, has a single helical profile designed to match the stator profile. The rotor rotation movement creates progressing cavities from bottom displacing the fluid through each successive cavity and consequently the pumping action. PCPs are non-pulsating positive displacement pumps and will deliver a constant flowrate for a given rpm of the rotor. The conventional PCP has the stator with the helical profile made of elastomer and glued to an external metallic tube (Fig. 1a). The rotor fits the stator with negative clearance. The metal PCP has the stator fully metallic and hence able to handle very high temperature (Fig. 1b). The stator is composed by 3 elements of 9 ft long welded together. The rotor fits the stator with positive clearance. Both are specially coated for high temperature and wear resistance, but the rotor serves as a sacrificial element. Although the metal PCP does not have the same interference fit between the rotor and stator as a conventional PCP, the efficiency is still adequate as the fit can be precisely adjusted using the patented hydroforming process used for manufacturing. It is also important to note that the absence of any elastomer material can provide the metal PCPs with an operational and run life advantage in applications where the downhole fluid environment causes severe swelling and/or degradation of the various pump elastomers that are available. The metal PCPs are tested with water to ensure volumetric efficiency; friction and dynamic torque are all within specification. The main advantages of the metal PCP include: - Easy flowrate control (proportional to rpm) - Easy to install (similar to conventional PCP) - High operating temperature range (up to 350 C) - Acceptable for high or low viscosities - Production with low bottomhole pressure - Non shearing and no formation of emulsions - Easy initial start-up at higher viscosities Figure 1. The conventional (a) and metal (b) PCP systems. (a) (b)
SPE 149944 3 KUDU PCM Vulcain offers three models of the metal PCP capable to cover a wide range of flow rates for heavy oil production: 400MET1000, 550MET750, and 1000MET500. The first number is for the maximum rate in m3/d at zero head at 500 rpm, while the second number gives the nominal head capacity in meters of water equivalent. The pumps are rated to 350 C. SAGD operation and PCP performance To date the majority of active in-situ operations have used SAGD for their recovery methods. The steam assisted gravity drainage process is an effective method for heavy oil and bitumen production utilizing two parallel horizontal wells, one above the other. The top well is steam injector and the bottom one is the oil collector. When steam is continually injected in the top well, a steam chamber forms in reservoir and grows upward to the surroundings displacing heated oil following gravity mechanism drain into producer (Fig. 2). Key factors to promote the use of SAGD are: - reservoir characteristics vertical permeability has to allow for steam chamber growth and flow to the producing well; sufficient cap rock to sustain bottom hole pressure needed to promote flow of bitumen; - steam oil ratio, meaning less energy spent per barrel produced; - recovery factor, leaving minimal quantity of oil in the reservoir when the well is abandoned. Figure 2. The SAGD recovery process. The B field is a shallow (about 300m TVD) low pressure oil sand field located in Athabasca oil sands of Alberta, Canada. The crude oil API is 8 with viscosity about 2 million cp at initial reservoir temperature of 12 C. The virgin reservoir pressure is 1500 kpa, around 5 Darcy permeability, 35% porosity, and 80% oil saturation (Tab. 1). Primary recovery from the B field is steam assisted gravity drainage. The horizontal wells were drilled together, an injector-producer well pair, with about 7 m of vertical spacing. The field has several well pairs under SAGD employed predominantly with 400MET1000, producing crude from McMurray formation. The typical well completion is shown in Figure 3a, b. (b) (a) Figure 3. The typical completion for SAGD well for ESP (a) and metal PCP (b).
4 SPE 149944 Table 1. Reservoir properties in McMurray formation. Reservoir pressure, kpa 1500 Depth to top of reservoir, m 200 Reservoir thickness, m 30 Vertical permeability (Kv), Darcy 5 Permeability ratio (Kh/Kv) 2,5 Porosity 0,35 Oil saturation 0,8 Oil viscosity 2 000 000 Reservoir temperature, C 12 Steam quality 0,95 Steam injection pressure,kpa 1900 Steam injection rate, m3/d (continuous) 700 Steam trap control, C 5 Injector-Producer spacing, m 7 water injection temp., C 235 SAGD Well pairs spacing,m 150 The production from SAGD at the B field started in 2006 with a pilot well pair initially equipped with beam pump, which was replaced later with a metal PCP. In the next year additional well pairs were drilled and equipped with ESPs. However at that time the efficiency of ESP in several wells had decreased due to often failures and they were converted to metal PCP. Currently all the wells are equipped with metal PCPs (Fig. 4). The overall field production is below expectations, due to overestimations of reservoir quality and production rate, producing about 600 m3/d instead of expected 1500 m3/d (Fig. 5). Figure 4. PCM Vulcain TM well pairs. Figure 5. Overall field production. The first metal PCP was run in Pad E well P4 in 2006 with 150 rpm. Initial volumetric efficiency was about 90%. During this start-up period of the SAGD well pair, downhole temperature was below 100 C. The lowest intake pressure at the pump was seen at 650 kpa (g). With the increase of pressure communication between injector and producer, pump intake pressure gradually increased to 1200 kpa (g), as well as the pump speed increased from 150 to 300 rpm. The bottomhole temperature rose to 180 C. After 6 months following the start-up, the production dropped to 50%, and it was decided to increase pump speed to 350 rpm. The fluctuating production increase for two months was followed by dramatic decrease, showing the volumetric efficiency of 30%. Since the operating pump speed was maximal due to possible vibration problems, it was considered to change pump to stronger model. Thus in the end of 2007 the 400MET100 metal pump was changed to 550MET750. Well production improved significantly up to 80 m3/d at 200 rpm, with 70% of pump efficiency. About six months later the well production dropped as the pump efficiency decreased. Therefore the pump speed was increased to 300 rpm. Accordingly crude production increased to previous level, while volumetric efficiency decreased to 50% (Fig. 6). Being the pilot well to test metal PCP, the performance of these pumps has exceeded expectations.
SPE 149944 5 Figure 6. Pad E P4 well production chart. Figure 7. Pump efficiency at Pad B P3 well. Another 40MET1000 metal PCP was employed in Pad B well P3. This PCP started production in 2007 and pump speed was quickly ramped up to 180 rpm and then gradually to 230 rpm, and later on to 380 rpm. Pump volumetric efficiency initially was considerably high at about 85%, but dropped to 60% and 47% with rpm increase respectively. Liquid flowrate reached 160 m3/d. About four months after ten days turnaround, the pump speed increased to 390 and 400 rpm, and the efficiency stabilized at about 55%. The bottomhole temperature reached the level of 180 C with a pump intake pressure of around 980 kpa (g). The liquid production made 190 m3/d at highest point (Fig. 7). The field trial of the first metal PCP in a low pressure SAGD operation has demonstrated that a PC Pump can successfully initiate the start-up of a SAGD well pair even at relatively low bottomhole temperature, what is a challenge for ESP due to high viscosity. Unlike to other SAGD projects, the B field wells are directly converted to pumping after the steam circulation. Using PC Pumps we may not to worry about keeping the well at hot temperature. It can cool down without compromising the start-up. The conversion to PC Pump allowed removing the need for live well interventions, saving time and reducing risks. Moreover, PCPs are very easy to control and flowrate can be set by adjusting only the rod speed at the variable frequency drive (VFD). This allows for a very precise control of the well behavior and makes well performance optimization possible. Pump sub-cool and reservoir sub-cool can be optimized with great accuracy so that bitumen production is maximized. Metal PCPs at the B oil field have demonstrated a very good performance with low pump intake sub-cool. However the volumetric efficiency of the metal PC Pump is challenging. Indeed it was confirmed that this efficiency could be significantly affected by the head applied to the pump, due to positive clearance necessary in this technology and its increase with wear. The metal PCP in P4 well performed an overall gradual efficiency decrease with time corresponding to normal wear. At the same time, the PC Pump in P3 well showed initially a very high efficiency, but dropped dramatically in a month, but with further stable production. Nevertheless, it should be mentioned that metal PCP production was higher compared to previous lift system, namely ESP (Fig. 8). After these perspective results, total number of fourteen metal PC Pumps were installed at the B field. Figure 8. The advantages of PCM Vulcain TM metal PCP over ESP.
6 SPE 149944 Summary The metal PC Pumps had produced for over than 15 months with total gross flowrates varying from 50 to 250 m3/day at speeds ranging from 150 to 400 rpm. The bottomhole temperatures had ranged from 100 C to 200 C. While the operating conditions varied significantly, an exceptional improvement in SOR (9 pre-lift to 2.8 post-lift) is associated with production optimization using the metal PCP. Also it is worth of mentioning that the B field had installed 14 metal PC Pumps with no failures (Fig. 9). The production forecast based on the metal PCP production performance and further SAGD operations shows the gradual increase of daily flowrate over 500m3. The overall field cumulative production is also predicted to reach 2,000 m3/d (Fig. 10). Figure 9. Metal PCP non-stop operating period. Figure 10. Production forecast for the B field. Conclusion To conclude, we can say that after more than 15 months operation, where the wells were steam injected at various operating speeds, pump loads, and fluid flowrates, the metal PCP has proven its versatility and influenced to improve well cash inflow. The high temperature package handled the wide range of viscosities, from low to high intake and differential pressures. Speed adjustment enabled to fit production and well capability as downhole conditions varied. References 1. Lea, J.F., Anderson, P.D., Anderson, D.G. Optimization of progressive cavity pumps systems in the development of Clearwater heavy oil reservoir, Journal of Canadian Petroleum technology, JCPT88-01-05. 2. Beauquin, J.L., Boireau, C., Lemay, L., Seince, L., 2005. Development status of a metal progressing cavity pump for heavy oil and hot production wells. Paper SPE-97796 presented at the SPE International Thermal operations and Heavy oil symposium, Calgary, Alberta, 1-3 November. 3. Beauquin, J.L., Ndinemenu F., Chalier, G., Lemay L., Seince, L., Damnjanovic, A., 2007. World s first metal PCP SAGD field test shows promising artificial lift technology for heavy-oil hot production: Joslyn field case. Paper SPE-110479 presented at the SPE Annual Technical Conference and Exhibition, Anaheim, California, 11-14 November. 4. Guerra E., Sanchez A., Matthews C., 2009. Field implementation experience with metal PCP technology in Cuban heavy oil fields. Paper SPE-120645 presented at the SPE Production and Operations Symposium, Oklahoma City, Oklahoma, 4-8 April. 5. Rae M., Seince L., Mitskopoulos, M., 2011. All metal progressing cavity pumps deployed in SAGD. Paper WHOC11-578 presented at the World Heavy Oil Congress, Edmonton, Alberta.