In recent years, the industry has shifted its focus toward developing unconventional and conventional tight-oil plays, which has led to a steep learning curve in the development and application of new technologies. This paper discusses the progression and findings of operators in a Canadian unconventional oil play, and how current techniques are providing operators with reduced stimulation costs and improved fracture placement, leading to higher initial production rates and cumulative production.
With the advancement of horizontal drilling and completion techniques, operators are revisiting oil plays that had previously been developed with vertical wells or unstimulated, horizontal wells. In many cases, these plays were uneconomic to pursue, except during periods of higher oil prices. With recent improvements in horizontal-stimulation techniques, operators are now finding that cost-effective stimulation methods can be applied that improve the economics of both conventional and unconventional plays.
In one Canadian light-oil play, coiled-tubing (CT) conveyed, openhole fracturing was used initially as a stimulation technique. Production gains were noted, but the water from an adjacent zone limited the effectiveness of this technique. Operators then proceeded to use openhole packer completions as a means of controlling the fractures. This method provided positive isolation between openhole compartments but limited the number of zones that could be completed as well as the options available for workovers following the fracture treatments. More recently, operators have successfully used monobore drilling and completion techniques with a CT-deployed straddle frac stimulation method, providing both economic and low-operational-risk wells at lower drilling and completing costs.
The benefits of the monobore drilling and completion systems are:
Reduced drilling time over other methods
Single-stage cementing options
Full-diameter wellbore simplifies completions.
Flexibility in number of intervals and spacing
Fracture treatments designed are to maximize zonal coverage
Ability to control fracture placement to avoid nearby water zones
Flexibility to alter job design during treatment
Ability to return to the well following the initial treatment for future treatments
Lower water requirements for stimulation
Reduced costs lessen environmental impact with reduced water volume
Reliable, proven, straightforward process
Compared to other methods, this monobore and CT-straddle frac system has provided a lower-risk, engineered approach for delivering higher initial rates and increased cumulative production throughout the life of the well. It has also lead to the development of tight-oil reserves located outside of the conventional production fairways.