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Clifford Louis completed his master's degree in petroleum engineering from University of Calgary in 2019. He is the author of five technical papers in international publications and has presented in many SPE conferences. Louis is the editor-in-chief for Fridays for Future–Youth Climate Activists, where he's researching on innovative methods of carbon sequestration and storage methods to mitigate global environmental challenges.
It is not unusual to compare a team of subsurface professionals to a team of detectives piecing together a sequence of events to solve a crime. To make sense of what is happening in a hydrocarbon reservoir, subsurface teams, like detectives, typically have incomplete, sparse data sets, sampled at different points in time and space. The data only provide a partial picture of what has happened and what is likely to happen in the future. In either case, surveillance is an essential tactic to build a mental model of the situation. Fortunately, both detectives and subsurface teams have growing surveillance toolboxes to help fill information gaps and narrow the range of possible scenarios.
Sand and other solids production can cause problems in PCP systems by accelerating equipment wear, increasing rod torque and power demand, or causing a flow restriction by accumulating around the pump intake, within the pump cavities, or above the pump in the tubing. Also, given its specific gravity of 2.7, even moderate volumes of sand can substantially increase the pressure gradient of the fluid column in the production tubing. Sand production is frequently a byproduct of oil production, especially in some primary heavy oil operations (e.g., Canada) where it is an important part of the recovery process. In such operations, sand influx is usually most severe during the initial stage of production when the volumetric sand cuts can exceed 40%. Subsequently, the sand cuts often stabilize at 3%.
Heavy oil is defined as liquid petroleum of less than 20 API gravity or more than 200 cp viscosity at reservoir conditions. No explicit differentiation is made between heavy oil and oil sands (tar sands), although the criteria of less than 12 API gravity and greater than 10,000 cp are sometimes used to define oil sands. The oil in oil sands is an immobile fluid under existing reservoir conditions, and heavy oils are somewhat mobile fluids under naturally existing pressure gradients. Unconsolidated sandstones (UCSS) are sandstones (or sands) that possess no true tensile strength arising from grain-to-grain mineral cementation. Many heavy oil reservoirs are located in unconsolidated sandstones.
Cold heavy oil production with sand (CHOPS) recovery processes generate large volumes of sand that must be managed. In Canada in 1997, approximately 330,000 m3 of sand (approximately 45% porosity sand at surface) were produced from CHOPS wells. Individual wells may produce as much as 10 to 20 m3/d of sand in the first days of production and may diminish to values of 0.25 to 5 m3/d when steady state is achieved. Sand grain size reflects most of the reservoir. There is little sorting or segregation in the slurry transport to the well; however, not all zones in the reservoir may be contributing equally at all times.
While typical production operations seek to prevent sand production, cold heavy oil production with sand (CHOPS) operations use sand production to increase overall productivity. This difference can create operational issues throughout the life of a CHOPS well. It has implications for monitoring strategies as well. To initiate sand influx, a cased well is perforated with large-diameter ports, usually of 23 to 28 mm diameter, fully phased, and spaced at 26 or 39 charges per meter. More densely spaced charges have not proved to give better results or service, but less densely spaced charges (13 per meter) give poorer results. More densely spaced charges may eliminate reperforating as a future stimulation choice because full casing rupture is likely to take place.
Cold heavy oil production with sand (CHOPS) is a relatively recent technology. As such, only a few case histories of its application over a number of years have been published. Nonetheless, those that are available provide insight into the application of this technology. A detailed Luseland field case history has been published. It had a long history (12 to 15 years) of slow production with reciprocating pumps, an attempt to produce with horizontal wells (6 wells, all failures), and then a conversion to CHOPS through reperforation and progressing cavity (PC) pump installation.
Plunger lift has become a widely accepted and economical artificial lift alternative, especially in high-gas/liquid-ratio (GLR) gas and oil wells (Figure 1). Plunger lift uses a free piston that travels up and down in the well's tubing string. It minimizes liquid fallback and uses the well's energy more efficiently than does slug or bubble flow. As with other artificial lift methods, the purpose of plunger lift is to remove liquids from the wellbore so that the well can be produced at the lowest bottomhole pressures. Figure 1--Plunger installed in Canada. In recent years, the advent of microprocessors and electronic controllers, the studies detailing the importance of plunger seal and velocity, and an increased focus on gas production have led to a much wider use and broader application of plunger lift.
A recent datathon held from April to June 2021 focused on the application of analytics and data science tools on oil and gas well-log data to assess geothermal potential in two North American basins. The 2021 Geothermal Experience Datathon (GTX 2021) was organized by a committee made up of members from the Society of Petroleum Engineers (SPE) Calgary and Gulf Coast Sections and Untapped Energy, a startup data-science organization. A datathon is an event where participants gather to solve practical industry-relevant problems by working in teams to generate insights and potential solutions. It serves as a platform connecting participants, organizations, and businesses for the purposes of upskilling, transferring knowledge, and exploring new problem spaces. Datathons, and the closely related hackathons, have increasingly become an important means of fostering collaboration and orchestrating activities between different parties along shared interests because of the network effects generated by their participation.