It is easy to install and the modular design of the system makes it customizable to any number of stages. Once installed, a rig is not required during stimulation operations, allowing for another well to be spudded immediately after setting the system. The StackFRAC® system allows for testing in areas outside of seismic mapping that can help clients understand the extension of the formation without acquiring more seismic data. This system is flexible and can be installed in vertical, horizontal or multi-lateral wells.
A standard Packers Plus StackFRAC® multistage completion system consists of a series of FracPORT™ sleeves and RockSEAL® packers. The system is isolated from the wellbore by dropping a ball that lands in a seat at the toe of the system. This allows internal pressure to be increased to hydraulically set the RockSEAL® packers, segmenting the open hole into multiple zones. Once the packers are set, stage-by-stage stimulation can be performed beginning at the toe of the well moving to the heel. The Hydraulic FracPORT™ in stage one is opened by further increasing pressure within the liner. All remaining stages are opened by pumping a ball onto a ball seat within each FracPORT™ sleeve to build pressure behind the ball and open the sleeve. Dropping successively larger balls allows for multiple FracPORT™ sleeves to be run in sequence. This is done in a single, continuous pumping operation, a standard practice with Packers Plus completion systems, which are modular, and designed based on the well requirements. This makes them flexible and able to adapt to any stimulation and testing program.
An operator working in the Ain Tsila field of Eastern Algeria used the StackFRAC® system in a 4-well pilot project to assess the potential for commercial production from the reservoir. The first well was horizontal and used a 4-stage system. The next two wells were drilled vertically and were slated to be completed with a single stage. The fourth well was horizontal and used a 2-stage system. The StackFRAC® system was chosen as the operator required a flexible completion that could be run in both horizontal and vertical wells and would permit hydraulic fracturing if needed. Drillable Closeable (DC) FracPORT™ sleeves were run in place of the standard FracPORT™ sleeves. The DC FracPORT™ sleeve can be shifted open with a ball as with the standard FracPORT™ sleeve, but can also be opened and closed as desired using a shifting tool run on coiled tubing with or without the ball seat in place. This enables pre- and post-stimulation operations such as production testing of individual zones, or water shut-off. In addition, all testing and stimulation can be done without a rig present to reduce operating costs as compared to the cemented liner method. The operator was able to obtain stage-by-stage, pre- and post-stimulation production results to prove gas reserves in the pilot project which was completed within the designated time and below budget. The production results from the field were better than expected and a full development plan is now underway.
Another operator planned to drill an exploratory well in a new area of the Mancos formation, USA. The Mancos is a mixture of shale, siltstone and interbedded clay. It is an unconventional formation with low porosity and permeability; however, natural fractures are present throughout. Historically, the Mancos was drilled vertically and completed with a single stage for fracture stimulation, resulting in marginally economic wells. More recently, the focus has shifted to horizontal wells using innovative completion technology to increase the success of the play. The operator decided to drill a horizontal well, since previous vertical wells were barely economic. The main focus was to test the production potential of the well in an economic way. The StackFRAC® open hole, multistage system completion was selected for the exploratory well as it would allow the operator to exploit the natural fractures present in the Mancos.
A 7-stage StackFRAC® system was designed and DC FracPORT™ sleeves were installed without ball seats for all stages. To manipulate the sleeves, a shifting tool was run on coiled tubing. The operator chose to do this because the sleeves were to be opened and closed several times and they did not want any balls present in the system. All seven stages were opened and allowed to produce for six months to establish a base line for unstimulated production potential.
Coiled tubing was then used to close all but the first stage of the completion system. The operator stimulated this stage, ran into the hole with coiled tubing to close the DC FracPORT™ sleeve, pressure tested the system to ensure it was closed, and then opened the next sleeve to allow for stimulation. This process was repeated until all seven stages were stimulated.
After stimulation, all seven stages were opened with a service rig for production. The well was then flowed back, producing 10 times more than the previously completed vertical wells. Even with the coiled tubing operations, the total stimulation time was only 30 hours and was done on time and on budget. Because the operation and results were a success, the operator plans to develop their Mancos formation assets using the StackFRAC® system.
The above case studies demonstrate the utility and the flexibility of the Packers Plus StackFRAC® completion system for exploration wells. If the operator decides that a zone requires stimulation, the StackFRAC® system is capable of delivering any type of stimulation treatment. After stimulation, the operator can choose to do more testing by shifting the sleeves as needed, or simply turn the well over to production. The flexibility of the DC Frac- PORT™ gives the client many options for testing, production, shut-off or injection.