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Information Only - Waste Isolation Pilot Plant - U.S. Department of ...

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ea"ons <strong>of</strong>ten do not yield a production history which is suitable for decline-curve<br />

analysis (see Kloepper, 1993). Ultimate recovery was not calculated for these wells. A<br />

few wells did not yield data that supported calculation <strong>of</strong> ,wn or<br />

unrecognized factors have left these wells with an erratic productio: 3tOry, Ultimate<br />

recovery was not calculated for these wells.<br />

After ultimate recovery wa~ "3lculated for individual wells, the average ultimate<br />

recovery per well Ii" . calculatedh major pay zone in pools adjacent to the WIPP<br />

land withdrawal area by the met!~ _,,'med below, This concept <strong>of</strong> the average well is<br />

widely used in the petroleum industry (see Holmes et aI., 1985). Although the concept <strong>of</strong><br />

the average well is not suited to estimate resources for anyone particular prospect, it can<br />

be used with confidence to estimate the.resources under an area such as the WIPP site,<br />

which consists-<strong>of</strong> multiple undrilled prospects in known hydrocarbon traps that are<br />

projected to extend underneath the site.<br />

In order to calculate averac" Jltirnate recovery. a production decline curve for the<br />

average or typical well in each pool was established. The method u:;ed to generate this<br />

typical decline curve was dependent upon the quality and quantity ~roduction data<br />

available in each pool. For Delaware pools, montL production were assembled for<br />

all wells for which ultimate recovery was calculated. Data were normalized to the first<br />

month <strong>of</strong> production for each well. Then, the average production for each month<br />

(normalized to the well's initial nroduction) was calculated. Basedm these normalized<br />

average monthly production values, an average dec;.. ne curve for wells in each oil and gas<br />

pool was calculated according to the method descrd above. For pools in formations<br />

other than the Delaware, construction <strong>of</strong> the typical decline curve is described under<br />

discussion <strong>of</strong> each pool.<br />

Petroleum resources underneath the WIPP land withdrawal area and the surrounding<br />

one-mile additional study area \ ~ calculated for each oil and gas pool projected to<br />

extend underneath these areas (T~ .. 2-4). The potem.:al.iy productlve area for each pool<br />

was mapped by using the struetlm and stratigraphic maps to project boundaries <strong>of</strong> the<br />

traps from drilled producing areas into undrilled areas. Productive area was calculated in<br />

terms <strong>of</strong> proration units based on a spacing consistent with that in the pools adjacent to<br />

the WIPP land withdrawal area (Tables 2-4). The number <strong>of</strong> proratlGn units was then<br />

multiplied by the average resources per well to estimate the total ultimate recovery for<br />

each pool in the WIPP land withdrawal area and in the additional study area. Resources<br />

<strong>of</strong> the pool are then equal to the ultimate recovery minus the cumulative production.<br />

The petroleum geology and petroleum engineering characteristics <strong>of</strong> productive<br />

and potentially productive strata beneath the WIPP land withdrawal'",-ea are described<br />

below, as is the history <strong>of</strong> oil and gas dri11ing and production in the area. The geology <strong>of</strong><br />

each stratigraphic unit and <strong>of</strong> the separate oil and gas pools within each stratigraphic unit<br />

is unique. The discussion is divided accordingly.<br />

XI-8<br />

<strong>Information</strong> <strong>Only</strong>

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