During the 1992 facilities turnaround of the Countess Upper Mannville "UU" Pool pressure buildup data was obtained from two vertical wells and one horizontal well. The relatively high permeability of the sand and the proximity of the horizontal well to the top of structure predetermined a lack of early time radial flow response from the horizontal well buildup analysis.

The analysis of vertical well buildup response in an offsetting vertical well and information acquired from log and 3-D seismic enabled the generation of a preliminary reservoir model from which the horizontal interpretation could be initiated. This model was refined until a reasonable match was obtained from the horizontal buildup data. Good agreement was achieved between the vertical and horizontal analyses.

By utilizing this offsetting data set in the horizontal analysis, a better quality, higher confidence interpretation was achieved. Benefits and limitations of this interpretation technique are discussed.


Pressure transient analysis techniques have progressed significantly in the past fifteen years due to improvements in diagnostic methods through use of the pressure derivative, through rigorous integration of specialized analysis techniques to calculate total interpretation model behavior, through the improvements in pressure gauge accuracy and resolution, and through the increases in available computer power. The limitations of manual techniques such as semi-log methods or type curve matching have been transcended by state-of-the-art integrated computerized analysis methods which have greatly reduced the uncertainty f pressure transient analysis results and the man-lime required to achieve expert level solutions.

In the 1990's, the analysis of most classical configurations of wellbore, reservoir and simple outer boundary solutions as been reduced to a simple process for well test analysis specialists. However, coincident to these well test analysis advances, additional research has produced theoretical solutions for an increasing number of complex well and reservoir geometries found in the field. The increasing complexity of pressure transient solutions for composite odels on certain applications produces more solution parameters than unique diagnostic regions on which to tune the variables on an independent basis.

Breakthroughs in horizontal well drilling and completion has promoted the successful application of this well orientation to both virgin and mature reserves in North America and throughout the world. The increased productivity from the large horizontal well section within the reservoir bas permitted the exploitation of reserves previously considered to be beyond economic reach. In addition, horizontal wells have been proven to improve weep efficiencies in secondary recovery processes in mature pools.

The pressure transient behavior of the horizontal well geometry has been determined by various authors such as Daviau 1, Goode (2,3), and Kuchuk (4,5,6), among others. The application of this theoretical approach to horizontal wells in multi-well pools is the subject of this paper.

Anatomy of the pressure transient behavior of an ideal horizontal well

The log-log plot of the pressure and pressure derivative profile from an ideal horizontal well producing a single phase fluid from an infinite-acting homogeneous reservoir is set out in Figure la. The transient behavior can be sub-divided into five regions.

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