Jared Wynveen, P. Eng McDaniel & Associates Consultants Ltd. 2014

Transcription

1 Jared Wynveen, P. Eng McDaniel & Associates Consultants Ltd. 2014

2 Subcool Basics Idealized Subcool Real World Subcool Subcool Visualizations Subcool case study Subcool Management - New Technology Outflow Control and Steam Distribution Inflow Control Devices Closing Remarks

3 Subcool refers to the liquid level above the producing well Subcool is important because it prevents steam from short-circuiting into the producing well LIQUID POOL Subcool is measured by the difference in temperature of the produced fluids to that of the steam chamber A larger temperature difference implies a larger pool of liquid as the source of the heat (the steam chamber) is further away from the producer As a rule of thumb, every vertical metre of fluid increases subcool by 10 C

4 Ideally, we would like a uniform low subcool along the producing well Steam Injection Steam Injection Injector Producer OIL RATE A low subcool provides the best productivity and steam-oil ratio Subcools below 0 o C while potentially advantageous to productivity are not feasible due to pumping limitations of steam SOR High subcools lead to a reduced area where mobile bitumen can be produced resulting in lower productivity and higher SORs Subcool o C Vander Valk P.A., Yang P., Investigation of Key Parameters in SAGD Wellbore Design and Operation, JCPT, June 2007, Volume 46 No. 6

5 In the real world, subcool is variable along the well-pair, resulting in inefficiencies and poorer performance The impact of subcool management on well-pair conformance and performance is even more dramatic as we move away from developing only the best SAGD reservoirs Due to pumping limitations, i.e. inability to produce large amounts of steam, production is limited by the hottest point of the well-pair Many companies have recently talked about hot spots along well-pairs, these are essentially areas of preferential fluid flow and little to no subcool CNQ Wolf Lake Southern Pacific MacKay CVE Pelican Lake Pilot

6 Below is an image of a typical subcool profile: low Subcool at steam injection points (short and long injection strings) and high subcool in the center of the well-pair High Pressure, Low Subcool Low Pressure, High Subcool High Pressure, Low Subcool Below is an image of a reservoir where the reservoir at the toe is more permeable than at the heel High Pressure, Low Subcool Low Pressure, High Subcool Great Reservoir, Bitumen accumulating, High Subcool

7 Below is an image of a single point breakthrough or hotspot In this example, only a small portion of the well-pair is being produced effectively leading to materially lower productivity Hotspot Below is an image of a reservoir where the reservoir at the toe is much higher than the heel, resulting in very high subcool at the heel Injector partially flooded, Inefficient production and injection

8 Pad 8 at Long Lake (CNOOC-Nexen) has historically had low average well-pair productivity and high SORs Pad SORs were generally in the 6 to 8 range and average well-pair productivity was approximately 300 to 400bopd/well-pair Due to the high SOR and poor productivity, 2 of the 6 wells were shut-in in mid-2012 In 2013, the operator completed manual oil cut tests and found better results than expected The positive tests prompted the operator to invest in minor surface facility improvements and carry out prolonged production testing to verify the results of the manual testing In line with operational improvements implemented in other areas of the field, the operator decided to operate the wells more aggressively and with a lower subcool After a period of drawdown, oil cuts and oil rates increased significantly Based on the initial positive results, the well-pairs that were previously shut-in were reactivated and now produce considerable amounts of oil

9 Pad 8, roll-up of well-pairs 5 & 6 Oil rate increased 3X and SOR decreased by 60%

10 Pad 8, total roll-up including previously deactivated well-pairs

11 Recognizing that subcool management is an important and ongoing concern for all SAGD producers, there are a number of new technologies that may assist in optimizing subcool and improving reservoir performance Outflow Control Devices (OCD)/Steam Distribution Systems Inflow Control Devices (ICD) Commercialization of these technologies is particularly important to companies that have existing well-pairs with poor wellbore conformance and for the future development of less ideal reservoirs Also important but less critical is the performance improvement that can be achieved in Top-Tier reservoir

12 The purpose of OCDs and Steam Distribution Systems is to more evenly distribute and regulate steam injection along the well- pair Pressures/injection along the injector can be regulated in order to direct steam to less developed areas A more homogeneous distribution of steam leads to a more even subcool along the well-pair Before High Pressure, Low Subcool Low Pressure, High Subcool High Pressure, Low Subcool After High Pressure High Pressure High Pressure High Pressure High Pressure

13 Incremental Productivity

14 ICDs are used as a direct means of homogenizing subcool along the producing well They reduce fluid intake velocity via back pressure Steam Injection Steam Injection Although there is more than one type of ICD, the ICD of choice for most companies has been the Baker Hughes Equalizer The Equalizer allows for optimum subcool management (approaching 0 o C) while at the same time restricting steam production The Equalizer has resulted in higher rates, lower SORs and better well-bore conformance at producing pilots In theory, the equalizer should allow for more aggressive drilling trajectories and greater resource recovery

15 Equalizer Well-Pair Adjacent Well-Pairs

16 STP has installed three ICDs to-date in an attempt to initiate higher wellbore conformance, reduce the impact of hotspots on subcool management and improve productivity Early results from the most mature well-pair are very encouraging (below) Results from two other wells not yet understood ICD Installation

17 Subcool management is now recognized as a critical component to SAGD production performance Inability to properly manage/optimize subcool may result in materially poorer performance than what the reservoir is capable of As industry moves away from developing only the very best reservoirs, subcool management will be even more critical to the success of a new project Technological advancements such as the Equalizer may allow for easier subcool management in less ideal reservoirs and improve performance expectations for SAGD in general

18 Jared Wynveen, P. Eng McDaniel & Associates Consultants Ltd. 2014