Three wells have been successfully drilled, cemented and fracture stimulated in the Kenai Gas Field utilizing an industry unique Casing-Conveyed Perforating System (CCPS). This revolutionary system consists of perforating guns external to the casing and integral valves in the casing for zonal isolation while fracturing. During completion operations all downhole equipment is remotely actuated without wellbore intervention. In addition, downhole sensors were run on all three wells providing monitoring of bottom-hole pressures and temperatures during cement operations, as the cement cures, during stimulation operations, and ultimately over the productive life of the well.
Special characteristics of the CCPS, such as the need for precise depth control and irregular geometry, present a unique set of drilling and cementing challenges compared to conventional casing strings. For the case history wells reviewed in this paper a total of 43 perforating modules have been deployed with 15, 12 and 16 modules run in the KBU 42–7, KBU 24–6 and KBU 44–6 wells respectfully. Meticulous pre-planning by a multi-disciplinary team of professionals provided solutions to the many challenges encountered. This paper provides detailed descriptions of the three CCPS wells drilled to date in the Kenai Gas Field, including the drilling, running and cementing requirements and the solutions developed and utilized in field operations. Each of the three CCPS wells completed to date has been deemed engineering, operational and economic successes.
Field / Reservoir Description
The middle and lower Beluga sands in the Kenai Gas Field are a normally-pressured 1,700' (520M) section characterized by stacked pay with highly variable pay quality. These fluvial sandstones are 5 to 30 foot (1.5M - 9M) thick. Permeability ranges from 0.01 to 3 millidarcies. Mineralogy is complex, including a high percentage of clays, volcanics, coals, and fines as described in Table 1. The framework grains for the Beluga sandstones are metamorphic rock fragments. The sandstones are bounded by discontinuous shale, siltstone, and coal beds. Formation gas is very lean (specific gravity = 0.56) with no condensate, and formation waters contain approximately 5,000 mg/l total dissolved solids. Recovery from the middle and lower Beluga formation in the Kenai Gas Field through 2001 is 51.6 BCF with estimated 260 BCF OGIP.
Conventional completion techniques were not optimally developing the Beluga Sand resource in the Kenai Gas Field. The CCPS was employed to improve ultimate recovery and life-of-well economics from this resource. The numerous benefits of the CCPS in this environment have been previously documented.1,2
Casing-Conveyed Perforating System Technology
The CCPS was designed to improve stimulation of productive intervals by allowing individual zone stimulation in a rapid, cost effective manner. To date eight wells have been drilled and completed in North America with the locations, number of modules, maximum deviation and dogleg severity detailed in Table 2. The casing string contains integral isolation devices, perforating guns external to the casing, and methods to fire the guns and actuate the isolation devices remotely. Figure 1 shows a schematic of a portion of the wellbore in which a second interval is being perforated and the isolation valve actuated.
