--> --> Abstract: Determining Reservoir Heat Content in Sedimentary Rock from Oil Field Temperature Data – First Approximations, by Richard J. Erdlac; #90124 (2011)

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Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Determining Reservoir Heat Content in Sedimentary Rock from Oil Field Temperature Data – First Approximations

Richard J. Erdlac1

(1) Erdlac Energy Consulting, Midland, TX.

Developing an oil and gas prospect requires the assessment of the in-place oil or gas for estimating resource value and its acquisition cost. Traditional geothermal energy through fracture and fault trends as the primary conduit for hot water from an unknown depth make this determination far more difficult. However, the initial determination of geothermal energy within a sedimentary reservoir can be accomplished using known equations of aquifer thermal capacity, the heat capacity of water, rock density, porosity, and relating these values through the volumetric method for determining the heat carrying capacity within the sedimentary rock. This provides an initial heat energy content and is the first approximation for resource determination. Unlike oil or gas, heat energy is not a finite resource trapped within a porous reservoir, but rather is a dynamic quality that will replenish itself over time. Thus this approach is only an initial approximation of the in-place heat. The nature of the surrounding rock and heat migration rate must be considered in a more long term analysis to establish the optimum energy generation procedures appropriate for any given thermal energy acquisition site.

To establish the evaluation approach, BHT data acquired from previous studies of the deep Delaware and Val Verde Basins of West Texas is being used to test these conceptual methods. A database of around 5,000 wells and over 8,000 temperature-depth (t-d) points provides the source for subsurface temperature data. Additional information on Permian Basin water types provides information that relates the salinity to the density of the produced water. Reeves County, in the northern part of the Delaware Basin in Texas, was chosen to initiate this next phase of geothermal investigation.

Many of the wells had multiple temperature readings within a hole. This provided an opportunity to test the difference in temperature calculations at specific depth intervals using a linear and nonlinear approach, an important consideration when calculating the suspected temperature within a specific target reservoir. Contour maps can then be generated at constant depth or within a specific target reservoir to determine how temperature varies spatially. This information, when complete, leads to development of a resource management plan over long term field production.