The demand for more efficient, effective, and environmentally acceptable hydraulic fracturing solutions will continue into the future as shale reservoirs play more of a critical role in meeting the rising energy demand. The measurement of success for tomorrow's wells will not just be improved operational efficiency and initial production, but will include long-term well performance and reduced environmental impact. Operators and service companies must remove the uncertainty associated with conventional hydraulic fracturing techniques and aim simply to generate the desired number of fractures while ensuring that proppant is placed accurately to achieve good conductivity for the life of the well. Some of the disadvantages of conventional well stimulation methods include the following:
This paper presents a coiled tubing (CT) fracturing solution designed to eliminate these issues, while also delivering a new level of treatment flexibility by using real-time control of rate and proppant concentration at the perforations. This new approach to hydraulic fracturing reduces hydraulic horsepower requirements and reduces overall water usage significantly, while maximizing the return on investment (ROI) for the operator.
The Canadian energy sector pioneered and developed industry-leading oil- and liquids-rich reservoir acidizing technology. This involved new acid additive chemistry and completion techniques. However, many of the newer technical professionals in the industry have not been exposed to this technology. The first section of this paper outlines acidizing technology, with a focus on application to current new opportunities.
Many of the current oil- and liquids-rich plays involve naturally fractured carbonate reservoirs. Acid treatments designed to enhance the conductivity of the existing fracture system can provide more-effective reservoir drainage than proppant fracturing treatments. The second section of this paper discusses how new placement techniques can offer more-effective zonal isolation while reducing completion time and associated costs, and how acid pre-pads can also reduce breakdown pressures and help minimize near-wellbore (NWB) tortuosity effects in many shale and sandstone reservoirs.
Lessons from The Past
Acid Blend Design Considerations
1. Acid types and applications.
2. Iron-induced sludging and additive dispersibility.
3. Non-emulsifiers/antisludging agents.
4. Testing procedures.
5. Iron-sulfide precipitation.
6. Corrosion of metals.
7. Corrosion inhibitors.
8. Sulfide stress cracking (SSC).
10. Wetting agents.
12. Fines migration.
13. Paraffin and asphaltene precipitation.
14. Scale precipitation.
15. Additional additives.
The challenge in recovering hydrocarbons from shale rock is its very low permeability, which requires cost-effective fracturestimulation treatments to make production economic. Technological advances and improved operational efficiency have made production from shale resources around the globe far more viable; however, while the wells being completed today are proving to be reasonably economical, the question that remains is if the operators are truly capitalizing on their full potential. In recent years, the industry has been in search of a better method to enable well operators to capitalize on the natural fractures commonly found in shale reservoirs. If properly developed, these natural fractures will create a network of connectivity within the reservoir, potentially improving long-term production when they have been propagated. In most shales, however, the stress anisotropy present can prevent sufficient dilation of the natural fractures during stimulation treatments. To induce branch fracturing, far-field diversion must be achieved inside the fracture to overcome the stresses in the rock holding the natural fractures closed. Increasing net pressure during the treatment will enhance dilation of these natural fractures, creating a complex network of connectivity, and the greater the net pressure within the hydraulic fracture, the more fracture complexity created.
Most of the various processes introduced previously are limited because multiple perforated intervals or large open annular sections are treated at one time. Also, to achieve the high injection rates required, they are treated down the casing, so that any changes made to the treatment require an entire casing volume to be pumped before these changes reach the perforations. This paper presents a case history of a multistage-fracturing process that allows real-time changes to be made downhole in response to observed treating pressure. This functionality enables far-field reservoir diversion to be achieved, ultimately increasing stimulated reservoir contact (SRC).