Unconventional Multiple Fracture Treatments Using Dynamic Diversion and Downhole Mixing

Abstract

Abstract This paper reviews a unique, relatively new stimulation process that uses dynamic fluid energy (instead of mechanical methods) to isolate treatment fluid flow to a specific fracture point along the wellbore. A process of hydrajet-fracturing has been developed by merging four existing technologies: hydrajetting, hydraulic fracturing, jet pump technology, and dual-path fluid injection. These have been meshed to create a method whereby a wellbore is perforated (if necessary) and a fracture is initiated and placed accurately at a specific location, and then soon repeated at another chosen location uphole, or closer to the heel when in a lateral wellbore. The process was later expanded as a hydrojet-squeeze stimulation method also, even to the point of applying both of these applications while stimulating a single wellbore. This process employs two independent fluid streams: one in the treating string and another in the annulus. As these fluid paths will be supplied with separate pumping equipment, we have the option to instantaneously alter the downhole mixture that is being used to treat the formation at the current location of the jetting tool. An additional use of this two-stream feature is the capability to pump two different fluids that can be mixed downhole with a tremendously high energy to form a homogenous mixture at the fracture entry point, even creating foamed fluids insitu for some applications. This technique has been used to stimulate more than 50 horizontal or highly deviated wells (and a few vertical wells) as of the preparation of this paper, both proppant-laden fractures and fracture acidizing treatments. On average, more than 7 fractures were placed along a typical horizontal wellbore, typically several hundred feet apart without the use of mechanical sealing equipment. Additionally, numerous horizontal wells with higher permeabilities have been stimulated using the hydrajet-squeeze process alone. The diversion process follows a dynamic isolation approach that uses a high-velocity, high-energy jetted fluid. The process was originally developed for its unique stimulation capabilities in openhole horizontal wells, but has been extended to wells that have cemented or non-cemented liners, whether vertical, deviated, or horizontal and even to multilateral completions (or recompletions). This paper offers insight into many of these treatments, including the different well situations, design considerations, operations, and available results of the treatments. Possible unconventional approaches using this concept and a unique implementation in the field are also discussed. Introduction When an operator considers a horizontal completion in a low-permeability carbonate or sandstone reservoir, cost containment becomes a prime drilling and completion consideration. For many recent and currently planned projects throughout the world, the opportunity for openhole horizontals to give increased production per completion dollar economically may be what justifies the development of a new field or additional drilling in an existing field. Also, the re-entry of older vertical wells for horizontal recompletions may dictate that the completion is openhole because of hole-size limitations. The global reality that our industry seems slow to accept is that horizontal completions in low-permeability reservoirs usually require significant stimulation for achieving truly economic production rates. Many horizontal-drilling programs have been based on often incorrect assumptionsthat long openhole laterals will avoid the need for expensive stimulation treatments normally required for economic vertical-well completions in that reservoir. Hydrojetting, the use of water under high pressure, is a well known technique that many industries use to perform different tasks.1 These tasks include cleaning and preparing surfaces, placing cements, drilling, cutting, slotting, perforating, machining, grouting, mining, and even household uses such as car washing and dental hygiene. Sand-laden fluids can be used, or cavitating jets may be required. Jetting pressures have ranged from a few hundred psi to 60,000 psi.