Abstract

Anadarko Petroleum drilled two exploratory horizontal wells to evaluate a potential tight oil prospect in the Kinderhook sand of the northern Permian Basin. The key characteristics of the Kinderhook play include a viable source rock, the Woodford Shale, immediately below the Kinderhook sand which is a tight reservoir rock with good storage capacity (average porosity of 11%, average permeability of 0.1 md). The Woodford Shale also serves as a bottom seal for the play, isolating it from the underlying Siluro-Devonian reservoir rocks which produce from conventional traps throughout the area of interest. The overlying tight limestone of the Lower Mississippian Lime provides the top seal.

Analysis of well and seismic data indicated a prospect in Yoakum County where oil shows were present in nearly all penetrations of the Mississippian-aged Kinderhook sand, and production was established from one vertical well. This information indicated a potential stratigraphic trap in the Kinderhook which might be holding oil over a large area. In this area the Kinderhook sand is found at a measured depth of approximately 12,100 feet and is approximately 30 to 50 feet thick. The sand transitions to a shale to the north providing a potential up-dip lateral seal. The underlying Woodford Shale is approximately 50 feet thick.

After mapping the reservoir extent and structure at the top of the Kinderhook with well control and 3D seismic, two locations were chosen for horizontal test wells. The first test was in a down-dip position and the second test was located in an up-dip position. The down-dip well encountered very tight sandstone and poor mud log shows. This well was completed over a 1500 foot interval with five frac stages. The flow back resulted in a low oil rate (10 -20 BOPD) and the test was terminated after 36 days. Based on the low oil recovery and the poor mud log shows observed in the lateral, the Kinderhook sand was interpreted to be wet at this location. The up-dip horizontal well encountered much better mud log shows throughout the 5000 feet of lateral length. This well was completed over a 2400 foot interval with eight frac stages. The flow back period resulted in oil flow rates ranging from 40 to 190 BOPD. The test was terminated after 46 days with an oil rate of approximately 50 BOPD and a water rate of approximately 650 BWPD.

The Yoakum county prospect was deemed uneconomic based on the low oil production rates and high water cuts. The possible failed prospect elements include inadequate lateral seal for the stratigraphic trap, and inadequate bottom seal to contain the fracture stimulations from reaching water-bearing Siluro-Devonian reservoir rock.