A new technique has been developed to stimulate heavily damaged, high-permeability wells that cannot be successfully acidized. Many sandstone producing formations in the ASIA-PACIFIC region fall into this category, for a variety of reasons.
The technique restores productivity in damaged wells by providing a very short, highly conductive fracture through the damaged area around the wellbore. Given adequate fracture conductivity, combined with enough length to ensure the fracture penetrates virgin formation permeability, production can be restored to levels greater than a well's natural capacity to produce in its undamaged state. produce in its undamaged state. This paper includes a discussion of some of the well conditions that can indicate a good candidate for the new application, as well as guidelines for designing the treatments. The technique is not easily modeled with conventional fracture simulators, but simple volumetric determinations have been used successfully to select effective treatment sizes. Two case histories are documented, plus the design considerations for two additional cases. The examples include applications for a variety of well conditions.
Acid stimulation of wells producing from damaged sandstone formations is not always successful Some formations are naturally acid-sensitive because of their mineral content, and numerous other problems can exist that are not easily addressed by matrix acidizing. A new technique has been developed, and successfully applied in the Asia-Pacific area, which allows restoration of predamage production levels, even in wells which cannot be acidized. This is achieved by creating a highly conductive propped fracture through the damaged area around the wellbore and into virgin formation permeability. This process bypasses the flow restriction caused by permeability damage and eliminates the need for radial flow conditions around the wellbore. The process can be applied regardless of the cause of process can be applied regardless of the cause of production loss. production loss. Since the technique is applied as an alternative to conventional matrix stimulation, it should be considered only for those wells where matrix treatments could provide economic returns. In general, this means that formation permeability must be high enough to allow (1) economic levels of production, and (2) matrix injection of treatment fluids at reasonable pump rates. When natural permeability is too low for these conditions, conventional hydraulic fracturing is more likely to offer economic returns from stimulation.
While permeability is the most critical factor in determining whether a well is a good candidate for this new stimulation technique, other factors must also be considered. If matrix acidizing has proved successful in a field, the only reason to proved successful in a field, the only reason to experiment with the new process would be economics; in some cases, the process can be performed at less cost than a large matrix acid treatment. Its routine application, however, should be limited to those fields where the cause of low production rates cannot be corrected with conventional acid treatments. Several conditions can lead to this situation.