Characterization of reservoir deliverability is fundamental for the economic development of any field. In the Bakken, there is a need for reliable pressure transient tests to provide the effective formation permeability of the fracture-matrix in this formation for deliverability calculations. This effective permeability can then be compared to laboratory measured core permeability of the matrix rock samples. This comparison is the basis for planning early production options and subsequent enhanced oil recovery (EOR) decisions. This comparison is particularly important because of the influence of massive hydraulic fracture stimulation on reservoir performance.

Determining well deliverability potential by conventional drill stem tests (DST) or traditional wireline formation tests in the past has resulted in mixed success in the Bakken. On the other hand, the mini-DST has definitely increased reliability and the success rate of pressure transient tests. The operation of mini-DST tool requires much less time than the classic DST, and multiple zone tests can be conducted to assess individual zone deliverability. The Mini-DST tool uses the conventional Wireline Formation Tester configured with a dual-packer module and downhole pump. Tests are conducted by inflating the dual-packer module to isolate a 3-foot interval of the wellbore. The formation fluid is pumped out from the packer-isolated wellbore interval to conduct pressure drawdown and buildup tests in the interval. An overlay of all the pressure drawdown and buildup results from various intervals is compared on a single plot to identify the most productive interval. Finally, conventional pressure transient analyses are performed to interpret all pressure drawdown and buildup tests. In this paper we present several field tests which were analyzed both by the above procedure as well as by numerical simulation.