Anadarko Basin Morrow-Springer Sandstone Stimulation Study
Authors: Simon D.E. , Kaul F.W. , Culbertson J.N. 
Published: December 2007

The Morrow-Springer formation is characterized by seven reservoir rock lithologies. Laboratory studies, including regained-gas permeability, SEM, petrographic, and X-ray diffraction, indicate that certain treatment fluids petrographic, and X-ray diffraction, indicate that certain treatment fluids are less damaging to a particular lithology than others. Developing lithology descriptions for this formation meant that treatments could be recommended without having to core every well.

Introduction
The Morrow-Springer sandstone of Lower Pennsylvanian/Upper Mississippian age is synonymous with stratigraphic gas and has turned the Anadarko Basin into a major gas producing area since the late 1960's. This has led to gas exploration being conducted more deeply in the Anadarko Basin. Gas from deep, continuous areas across the basin is being produced; estimated reserves of 10 to 50 Bcf (0.283 to 1.416 Gm3) gas per well are not uncommon. However, the Morrow-Springer reservoir sands must be stimulated hydraulically for commercial production. Anadarko Basin Morrow-Springer sandstone was studied because these reservoirs must be stimulated for commercial production and because little is known about formation and treatment fluid interactions or associated completion problems. This study determines the type of stimulation treatment fluid to be used with individual reservoir rock lithologies needing treatment. Several questions guided the study. Is reservoir lithology a factor in how much formation damage may be caused by stimulation fluids? Why does a stimulation fluid give good results in one geographic area but not another? Are the Morrow-Springer reservoir lithologies similar enough so that one fluid may be used for all? Are certain stimulation fluids more compatible with reservoir lithologies than others? More knowledge about the overall geology, depositional history, and stimulation practices of the Morrow-Springer formation was needed. Necessary background data (including Morrow-Springer cores, electric - logs, sample cuttings, stimulation treatment, bottomhole pressure, and drillstem test data) were gathered from 4 selected wells. Reservoir core samples were identified and cataloged into distinctive lithologies and analyzed for physical, chemical, textural, and mineralogical makeup. The cores were tested for formation-damage evaluations using regained-gas permeability tests, and petrographic and scanning electron (SEM) permeability tests, and petrographic and scanning electron (SEM) microscopes. Evaluation of all gathered data was used to recommend treatment fluids for each reservoir lithology tested. Some clay minerals can be misidentified if the morphology visible with the SEM is the only identifying criterion. Therefore, an energy-dispersive analyzer was used with an SEM to confirm mineralogical identification. X-ray diffraction analysis for mineralogy identification was conducted on the same samples examined with the SEM. This technique uses a powdered rock sample that yields information on the minerals present, but not their location in the rock.

Formation Depositional Characteristics
The Anadarko Basin is a large depocenter of sediments extending from southeast Colorado to south central Oklahoma.
JPT
P. 683