Steam-assisted-gravity-drainage (SAGD) processes become effective only after thermal and hydraulic communication between an injection and production well has been established during the startup operation of the well pair. Conventional steam-circulation startup operations typically take 2 to 3 months to achieve interwell communication, but reductions in the startup time can have a favorable impact on project economics. Enhancement of interwell permeability using fluid-injection (water, or steam, or solvent) strategies to promote geomechanical dilation of the oil sands has been proposed as a startup technique. These fluid-injection processes will produce complex interactions of thermal, geomechanical, and multiple-phase flow behavior in the interwell formation region. Understanding better the role that these interactions play in establishing well-pair communication will provide opportunities to improve SAGD recovery performance.
A triaxial experimental program has been designed and executed to explore whether cold-water injection would be sufficient to induce enhancements in effective permeability to water from geomechanical dilation mechanisms. Sample preparation techniques were modified to allow the preparation of reconstituted, very dense water-wet/bitumen sand specimens with different fluid saturations and almost identical porosities. Reclaimed/cleaned tailings sand from oil-sands mining operations was used to prepare artificial specimens, which are representative of McMurray Formation oil sands. A water-wet or bitumen sand core plug was then tested in an environmental chamber to simulate reservoir boundary conditions in terms of stress state, temperature, and pore pressure. A set of experiments was carried out in a triaxial cell under either initial isotropic or initial anisotropic stress state. Experimental results highlight the promising potential to dramatically enhance effective permeability to water and porosity in the dilated zone using cold-water injection at modest levels of stress anisotropy. The experimental results also provide support for the development of numerical models used in predicting SAGD startup performance and proactive utilization of the dilation as startup process for in-situ oil-sands development.
Thermal recovery methods, in particular technology based on steam injection, are used extensively around the world for heavy oil and bitumen production. Because of the unconsolidated nature of the majority of such deposits, sand control is required. Design effectiveness of sand control depends on the reservoir type, production technology and operational practices. The industry is facing many challenges such as low oil prices, tight environmental regulations, the need to lower risks while assuring well integrity and longevity and project economics. All of that requires special technical solutions for thermal well design, including sand control.
The paper provides an overview of sand control for thermal heavy oil and bitumen production operations, factors affecting sand control design for thermal projects, sand control devices and industry trends. Laboratory observations and field data are discussed. The impact of steam on different quality heavy oil and bitumen deposits in relation to sand control is discussed in detail. Efficient sand control design for thermal production operations requires a multidisciplinary approach and is an integral part of the well longevity and project economics. Better understanding of the impact of reservoir quality, thermal formation damage and operational practices on well performance is required to assure success of a thermal project.
When compared with steam-assisted gravity drainage (SAGD) operations in the McMurray Formation, Athabasca Oil Sands, SAGD projects in the Clearwater Formation at Cold Lake did not perform as expected, likely because of reservoir properties. This paper will use the Orion SAGD case study to: (1) investigate the impacts of reservoir properties on the SAGD thermal efficiency by field evidences; (2) identify key geological parameters influencing each well pad; and (3) summarize major geological challenges for Orion SAGD expansion.
Wireline log data were interpreted to characterize reservoir properties, which were used to build 3D models. 3D visualizations and 2D cross sections of the reservoir revealed spatial distribution and heterogeneity of each property. SAGD production performance was analyzed using: (1) temperature profiles that monitored the growth of the steam chamber; (2) cumulative steam-oil ratios (CSORs); and (3) oil production rates (OPRates), which are direct indicators of thermal efficiency.
Results show that impermeable barriers and low-permeability zones were detrimental to steam injectivity and steam chamber growth, as observation wells in Pilot Pads 1 and 3 did not detect any steam saturation. High-permeability zones favored high steam injectivity and mobility, especially in Pad 105. Steam chambers were irregularly shaped by high shale-content zones, as two sharp spikes displayed on the temperature profile in Pad 103. Low oil-saturation zones and thin net-pays increased the CSORs, as seen in Pads 106 and 104. Impermeable barriers are almost horizontal, making no difference on well pad orientation by their dip angles. Lack of porosity variation made it difficult to identify the impact of porosity on each well pad.
The relatively extensive distribution of impermeable barriers between and above well pairs, as well as the relatively large area of low oil saturation and thin net-pay, were identified as major geological challenges.
Steam-assisted gravity drainage is the method of choice to extract bitumen from Athabasca oil-sand reservoirs in Western Canada. Under reservoir conditions, bitumen is immobile because of high viscosity, and its typically high level of saturation limits the injectivity of steam. In current industry practice, steam is circulated within injection and production wells. Operators keep the steam circulating until mobile bitumen breaks through the producer and communication is established between the injector and the producer. The “startup” phase is a time-consuming process taking three or more months with no oil production. A variety of processes could be used to minimize the length of the startup phase, such as electromagnetic (EM) heating in either the induction (medium frequency) or radio-frequency ranges. Knowledge of the size of the hot zone formed by steam circulation and of the benefits of simultaneous EM-heating techniques increases understanding of the startup process and helps to minimize startup duration. The aim of the present work is to introduce an analytical model to predict startup duration for steam circulation with and without EM heating. Results reveal that resistive (electrothermal) heating with/without brine injection cannot be a preferable method for mobilizing the bitumen in startup phase. Induction slightly decreases startup time at frequencies smaller than 10 kHz, and at 100 kHz it can reduce startup time to less than two months.
Over the last 30 years, laboratory testing has been conducted to investigate the geotechnical properties of Clearwater clay shales from the Clearwater formation in northeast Alberta, Canada. These properties are important for characterization of the overburden zones above in-situ oil-sands mines and for assessment of caprock integrity in steam-assisted-gravity-drainage (SAGD) projects. In general, caprock-integrity assessments include caprock geological studies, in-situ stress determination, constitutive-property characterization, and numerical simulations, which allow operators to ensure that steam-injection pressure does not cause any risk to the confinement of steam chambers. The aim of this study is to identify and provide the representative parameters that can enhance understanding of the geotechnical behaviour of the Alberta Clearwater formation clay shale. Moreover, it illustrates how the results can be used to extract constitutive model parameters for modelling the behaviour of this class of material. The parameters are also used for complex reservoir-geomechanical simulation for caprock integrity. These parameters are also compared with other Cretaceous clay-shale counterparts in North America.
The Cold-Lake oil sands contain the second largest reserves volumes among the oil sands deposits in Canada. The bitumen and heavy oil are contained in various sands of the Lower Cretaceous Mannville Group - Clearwater Formation.
For the past 30 years, Cyclic Steam Stimulation (CSS) has been the commercial thermal recovery method employed in the Cold Lake area. More recently, Steam-Assisted Gravity Drainage (SAGD) has been field tested in number of pilot projects at Cold Lake. Although SAGD has been demonstrated to be technically successful and economically viable, questions remain regarding SAGD performance compared to CSS. A more comprehensive understanding of the parameters affecting SAGD performance in the Cold Lake area is required. Well configuration is one of the major factors which require greater consideration for process optimization.
This paper presents a numerical simulation investigation of the impact of using several modified well configurations for SAGD in the Clearwater Formation in Cold Lake area in order to improve the process performance. The technical feasibility of applying each arrangement was evaluated through sensitivity analysis using a fully implicit reservoir thermal simulator (CMG STARS 2009.13). In order to account for frictional pressure drop and heat losses along the wellbore, the fully coupled wellbore/reservoir (discretized wellbore) model was utilized during the course of this study. The reservoir and fluid properties were selected to represent the main bitumen production area at Cold Lake.
The new well configurations provide operational and economical enhancement to the SAGD process over the standard well configuration (a horizontal injector lying approximately 5 meters above a horizontal producer) in Cold Lake area. The SAGD process response to different reservoir parameters of the Cold Lake Formation, such as initial injectivity, mobile water saturation, and reservoir heterogeneity has been investigated for the most promising of the new well configurations.
Canada's oil sands are well recognized internationally, with Alberta's mined and in-situ oil sands reservoirs being well developed with mature commercial technologies. The next frontier in Canadian petroleum development will be the shallow in-situ oil sands residing in both Saskatchewan and Alberta. Presenting opportunities and challenges that are distinct from the mining and deeper in-situ reservoir situations, the shallow reservoirs will probably need to be developed with new "game-changer" in-situ technologies that will reduce and/or replace the use of steam and fresh water, and dramatically reduce the emissions of greenhouse gases, such as CO2. Significant research and development programs are now aimed at developing and demonstrating such new technologies. Piloting new shallow in-situ development technologies for Saskatchewan's oil sands deposits will enable a new source of Canadian "technology oil" and serve to test more environmentally friendly technologies that could be adapted to current commercial operations. This paper provides a detailed description of the oil sands geology and physical properties as well as highlighting Saskatchewan's oil sands and some of the novel recovery technologies that are being developed for shallow in-situ reservoirs.
Jiang, Qi (Osum Oil Sands Corporation ) | Yuan, Jian-Yang (Osum Oil Sands Corporation ) | Russel-Houston, Jen (Osum Oil Sands Corporation ) | Thornton, Bruce (Osum Oil Sands Corporation ) | Squires, Andrew (Osum Oil Sands Corporation )
The Upper Devonian Grosmont formation is a bitumen-saturated, carbonate unit located in Northern Alberta. It is considered to be among the world?s next largest unconventional oil resource plays. Since early 2006, there has been an increased interest in Grosmont resources exhibited by a range of companies, including super-majors.
Several in-situ pilot tests were conducted in the central portion of this area in the 1970s and 1980s, using steam and in-situ combustion processes. Similar to field tests in the McMurray formation oil sands before invention of the Steam-Assisted Gravity Drainage (SAGD) process, none of the early recovery technologies tested proved to be economic. Because the "gravity" drainage process has proved successful in commercial development of the McMurray formation oil sands since the mid- to late-1990s, the recovery potential for the Grosmont formation should be re-evaluated, based on improved recovery techniques.
Results from cyclic steam stimulation (CSS) field tests are compared and analyzed to understand the similarity and fundamental differences in reservoir properties between the McMurray formation oil sands and the Grosmont formation carbonate rocks. A preliminary interpretation is provided for laboratory test results for solvent processes applied to Grosmont carbonate cores. The scaling considerations from the laboratory results to field expectations are discussed. The paper also provides a direction for future studies and optimization opportunities for reservoir recovery leading to the commercial development of Grosmont carbonate reservoirs.
A new thermal recovery scheme is proposed that utilizes Steam-Assisted Gravity Drainage (SAGD) well pairs as well as Cyclic Steam Stimulation (CSS) wells placed in between the SAGD well pairs. The wells are operated in CSS mode until the steam chambers are in contact with each other and then switched to SAGD operation. It is shown that the new process recovers greater amounts of bitumen with lower injected steam in shorter operation time than is achieved with SAGD, Fast-SAGD and CSS.