Summary
Restimulation of wells completed in the Frontier Formation, a
low-permeability (e.g., 0.01–0.05 md) gas sand, has proved to be successful in
the Fontenelle Field. The field is east of the Fontenelle reservoir, on the
LaBarge Platform in the western part of the Greater Green River Basin in
southwestern Wyoming. In this area the majority of hydrocarbon reserves in the
Second Frontier are produced from the massive shoreface sandstones locally
known as the Second Bench of the Second Frontier (Kf22b).
To date, Berco Resources, LLC has increased reserves in the Fontenelle Field by
restimulating four wells producing from the Frontier Formation with massive
hydraulic fracturing treatments. Because of the success of these treatments,
another operator in an offset area to the north has also successfully
implemented a Frontier refracturing program. This paper summarizes the
refracturing program and the success which Berco Resources, LLC has realized.
The candidate selection process is examined, as well as operational
considerations when restimulating old wells. The stimulation treatments and
fluid systems are also investigated. Daily/monthly production data consisting
of gas, condensate, and water rates along with well head pressures are
evaluated for all cases with fractured well type curves, the pseudoradial flow
specialty plot (Δp/q vs. log t), and a production simulator comparing actual
versus modeled production rates. Finally, the impact of the refracturing
treatments on economic return is presented. The success of the refracture
treatments has led to a new drilling/completion program in the Fontenelle Field
in 2006 by an operator that recently acquired the Berco Resources, LLC
properties.
Introduction
Field Description. Fontenelle Field is approximately 75 miles
northwest of the town of Rock Springs, Wyoming (Fig. 1), on the southeast end
of the LaBarge Platform. The field, positioned primarily in T26N-R112W,
T25N-R111W, and T25N-R112W, encompasses nearly 120 square miles in both Lincoln
and Sweetwater counties. To date, production from the Fontenelle Field has been
271.77 Bcf gas and 525,563 barrels of oil from 343 wells. Production has come
mainly from the Second Frontier, but thin marine sandstones in the overlying
Baxter Formation have produced locally.
Geology. Deposition of the Cretaceous Second Frontier Formation, in
the Fontenelle area, began as lower delta plain muds, carbonaceous shales,
coals, and fluvial sands prograded over the poorly developed Third Frontier
shoreface facies, which represented the culmination of the Mowry transgression.
Sixty to seventy feet of lower delta plain sediment was deposited before a
relative rise in sea level flooded the lower delta plain environment. This
resulted in an abrupt change from the lower delta plain mudstones, siltstones,
and shales to offshore marine mudstones and siltstones. This transgression
marked the beginning of deposition of a thick, wave dominated shoreface
sequence which prograded eastward into the Cretaceous Interior Seaway and
contains the majority of the gas reserves in this part of the LaBarge Platform.
This shoreface sequence is known as the Second Bench of the Second Frontier
(Kf22b).
Gas production in the Fontenelle area comes primarily from the Second Bench of
the Second Frontier (Kf22b). This shoreface sequence consists of a 30 to 60
foot thick section that grades upwards from a very fine grained, bioturbated
sandstone to a more winnowed, medium grained sandstone. The top of the bench
often contains a very clean, high resistivity sandstone that varies in
thickness from zero to 20 feet. This is interpreted to be a clean, medium
grained sandstone deposited by distributary channels that have cut into the
underlying shoreface section. Permeability in these channels is generally an
order of magnitude better than the underlying shoreface section. The thick
shoreface sandstone is capped by the mudstones and carbonaceous shales of the
lower delta plain environment. The Frontier Formation, in the Fontenelle area,
conformably overlies the marine Mowry Formation and is conformably overlain by
the marine Baxter Formation (Robertson and Broadhead 1993). It is Cretaceous in
age and extends from upper Cenomanian to upper Turonian.
© 2008. Society of Petroleum Engineers
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History
- Original manuscript received:
7 July 2006
- Meeting paper published:
24 September 2006
- Revised manuscript received:
6 September 2007
- Manuscript approved:
9 October 2007
- Version of record:
20 May 2008
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