Maximizing Well Life and Optimizing Exploitation Strategies with Solid Expandable Tubulars
Workover operations are a fact of well maintenance that can range from a simple intervention to a costly remediation. Common global issues that warrant workover operations include correcting production or injection profile issues, converting wells from producer to injectors (or vice versa), correcting cementation problems, mitigating corroded casing, fracturing or re-fracturing zones, changing artificial lift methods, and perforating or re-perforating new or existing zones.
Taking into account the wells’ lifespan is decades long, well integrity is often compromised as flow of fluid conditions cause erosion and corrosion problems. This compromise in well integrity requires a workover strategy that maximizes the well’s life cycle. Solid expandable tubular systems are a proven technology that facilitates these types of strategies. Additionally, solid expandable systems support other enabling technologies and techniques such as smart completions, multi-fracturing strategies, steam-assisted gravity drainage (SAGD) applications, and unconventional enhanced oil recovery (EOR) strategies.
This paper explains how an operator with existing wells in northwest Texas conducted a workover program converting gas producers to CO2 injections. Because the oil in place had the potential to equal that of the remaining oil in the reservoir, the optimal approach would require a solution that prevented sacrificing hole size. Solid expandable tubular systems installed in more than 25 wells isolated the existing upper perforations and enabled injection through newly-perforated lower oil intervals.
CO2 injection remains an important EOR method in the US in spite of oil price swings and ownership realignments. This is especially true in the Permian Basin of West Texas and New Mexico. Over 95% of the CO2 flooding activity is in the United States, mainly in the mature Permian Basin of the southwestern U.S., and dominated by injection under miscible conditions. (Kulkarni et al, 2008) There are 1,673 reservoirs in the onshore lower 48 United States which are candidates for CO2 miscible flooding. These reservoirs were identified using the following criteria: (Kulkarni et al, 2008)
- API Gravity greater than 22 degrees.
- The reservoir pressure greater than the minimum miscibility pressure.
- Depth greater than 2,500 ft.
- Oil viscosity less than 10 cp.
- Current oil saturation is greater than 20% of the pore volume.
- Either sandstone or carbonate rock.
This paper discusses operational procedures to explain the workover strategy and its relationship with the exploitation strategy – which was to optimize final recovery of reserves and maximize the life cycle of existing assets.
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