Growing energy demand is leading the industry to re-evaluate resources found in challenging conditions such as unconventional formations. Cost-effective development of these resources depends upon strategic application of advancing production solution technologies. To enhance production and improve recovery processes, more efficient perforating and fracturing methods have evolved along with advancements in wellbore production hardware via use of solid expandable tubulars or combinations of solid expandable and conventional tubulars.
Expandable technology applied as a completion/production string provides an optimized or customized wellbore that can facilitate increased fracturing rates, resulting in improved conductivity and enhanced hydrocarbon production. A fully expandable or combination system with standard casing can provide an integral component in either new wells or re-entry wells where low-permeability reservoirs, such as those characteristic of unconventional formations, require isolation and separation for pinpoint hydraulic fracturing.
Although successful stimulation is routinely attained from hydraulic fracturing, ancillary downhole tools, such as conventional completion equipment, often compromise results by restricting flow and affecting pressure performance. Solid expandable swellable systems can optimize the fracturing parameters by maintaining larger diameters and providing positive seals for selective multi-zone isolation purposes. These production systems consist of expanded sealing sections in combination with expandable or conventional intermediate tubulars utilizing premium connections thereby providing a superior completion solution for mechanical diversion.
Right-sizing the wellbore to the reservoir can provide operators significant cost savings, even more so during these economic times. Utilizing larger diameter expandables in the horizontal wellbore allows operators to first optimize the fracture program to the potential of the reservoir then develop the well program to accommodate the fracturing rates and volumes as well as the surface pumping facilities. This can result in slimmer surface and intermediate sections at much lower cost without compromising the overall stimulation completion program nor planned production and recovery.
This paper will discuss the integration of expandable systems with other technologies and cite case histories to illustrate the effectiveness of solid expandable systems in enhanced production and fracturing applications.
A large percentage of the world's future energy demands will be fulfilled by unconventional natural gases that include tight gas, coalbed methane (CBM), shale gas, deep earth gas, geo-pressured gas, and methane hydrates. Unconventional gas reservoirs require the formation to be fractured by hydraulic means to improve the formation productivity by providing a conductive path and joining the existing fractures and cleats in the reservoir (Zahid 2007). Ultimate recoverable unconventional gas resources in the U.S. are estimated to be about 750 Tcf of which 170 Tcf are in coalbeds, 480 Tcf are in tight gas sand and 100 Tcf are in shale (Stark 2007).
The major unconventional gas reservoir types include tight reservoirs, CBM, shale's and hydrates. To some degree, there has always been production from unconventional reservoirs in virtually all North American basins in the United States such as Rocky Mountains, South and East Texas, north Louisiana, Mid continent, Appalachia, Jonah/Pinedale, Natural Buttes, Wilcox Lobo, Cotton Valley/Travis Peak, and Clinton/Medina. (Arukhe 2009)
Estimates of shale gas in the US range from 500 to 1,000 Tcf, while the Gas Technology Institute calculates ~780 Tcf. The US Energy Information Administration estimates that US shale's contain 55.42 Tcf in recoverable gas. Shale plays with potential occur across the United States from southern California through the Rocky Mountains, across the Midwest into the Michigan, Illinois, and Appalachian basins in the east and as far south as the Black Warrior Basin in Alabama. (Lyle 2007)