BMI/ONWI- i ONWI/SUB/84/E512-05000-T14 Hydrogeologic Investigations Based on Drill-Stem Test Data I Palo Duro Basin Area W Texas and New Mexico in Technical Report May 1984 E. Scott Bair Timothy P. O'Donnell Larry W. Picking Stone & Webster Engineering Corporation .m Prepared for IN Office of Nuclear Waste Isolation Battelle Memorial Institute 50; King Avenue Columbus, OH 43201 85R0408009 850222 - S_'-7-!= Ad tw., . - .... ,. ... God_ s - .--- .U .......... e., :. :BMI/ONWI- .... 't 7 .i e . K ~~~~~.Z. asede' oen v.....'-Der71Zltem r-7''l Test Data'*-; t0 .r'................... f:z-- 4 .4' vt; e, - t. --. i- /t * ir~ > 1 . ..- .-. ; . \. ..J isatD , ,;, ,.; - --, . , ,,f tSE)-''._o'^,.,.N,~~~~~,'-,..' .', X- 7-- BMI/ON WI- ONWI/SUB/84/E512-05000T14 Hydrogeologic Investigations Based on Drill-Stem Test Data Palo Duro Basin Area Texas and New Mexico Technical Report May 1984 E. Scott Bair Timothy P. O'Donnell Larry W. Picking Stone & Webster Engineering Corporation Prepared for Office of Nuclear Waste Isolation Battelle Memorial Institute 505 King Avenue Columbus, OH 43201 i ABSTRACT Drill-stem test (DST) data were compiled from wildcat wells and DOE- sponsored wells in the Palo Duro Basin area of Texas and New Mexico. The data were used to construct pressure-depth diagrams and to map regional potentiometric surfaces, based on equivalent freshwater heads calculated from initial shut-in pressures of the Wolfcamp and Pennsylvanian brine aquifers, the two regionally important deep-basin aquifers downgradient of the proposed repository host rock. Eighty percent of the 5,502 DSTs were screened from the data base containing DST data from various deep-basin geologic units because they did not comply with shut-in time and shut-in pressure agreement criteria. After screening, three sets of pressure-depth diagrams and potentiometric surfaces were constructed, corresponding to three levels of data refinement. The initial Wolfcamp and Pennsylvanian regional potentiometric surfaces, representing their present configuration, contained several local prominent mounds and depressions with unrealistic variations in flow directions and hydraulic gradients. Evaluation of pressure-depth data and oil and gas production data showed that many of the DSTs were performed in depressured oil and/or gas production zones, where formation pressures were reduced due to extraction of formation fluids. The low shut-in pressures recorded in these tests caused abnormally low heads to be calculated and contoured. Formation pressures recorded in these depressured zones represent local temporal pressures in a regional flow system that is probably steady state. Deletion of depressured DSTs produced potentiometric surfaces of the Wolfcamp and Pennsylvanian aquifers prior to oil and gas production, but still contained a few local prominent mounds and depressions caused by local aberrant DST data. Elimination of local grossly overpressured and grossly underpressured DST data, based on comparison of initial shut-in pressures and heads at a similar depth in the same geologic unit in the same well and/or adjacent wells, further refined the potentiometric surfaces. These surfaces probably closely approximate the regional configuration of the Wolfcamp and Pennsylvanian potentiometric surfaces prior to oil and gas production. Statistical analysis of the culling procedures showed that most of the refinement in the Wolfcamp and Pennsylvanian data sets was due to culling depressured DSTs. Some ii additional refinement was due to culling local grossly underpressured and grossly overpressured DSTs. Although almost all the DST data in the study area are underpressured relative to the range of probable hydrostatic pressure gradients, formation pressures measured in wells located on the High Plains are far more underpressured than formation pressures measured in wells located on the Rolling Plains. This probably is due to differences in the depth from the ground surface, across the High Plains/Rolling Plains escarpment, to potentiometric levels in the deep-basin strata. When the Wolfcamp and Pennsylvanian pressure-depth data are normalized to common hypothetical planes that eliminate the effect of measuring depth from varying topographic elevations, the underpressuring of High Plains and Rolling Plains data is similar. Normalizing the data to common planes also makes identification of abnormally pressured data more obvious because differences in topographic elevation are eliminated. iii TABLE OF CONTENTS Page I EXECUTIVE SUNHARY .1................................. I E............S I S ....................................... *..... ~ C -E-z..... ...................... .. 6 _.9 ............................................... 6 2.4 HYDROGEOLOGIC SETTING ......................................... 8 2.4.1 Regional Geologic Setting . ................... a 2.4.2 Hydrostratigraphic Units . 11 2.5 PREVIOUS INVESTIGATIONS ...................................... 16 2.6 COMPUTER PROGRAMS ............................................. 17 2.6.1 SURFACE II GRAPHICS SYSTEM .. 17 2.6.2 STATISTICAL ANALYSIS SYSTEM . 19 2.6.3 TRENDS .... 1.............................................1 ............................................. 20 ..................................................................... 20 2S P. ......................................... 20 S20 '..X-i~Ui"i~vwh................................. 23 al ........ 23 WI 4 WOLFCAMP AND PENNSYLVANIAN POTENTIOMETRIC SURFACES .26 4.1 GENERAL .2 4.2 INITIAL WOLFCAMP AND PENNSYLVANIAN POTENTIOMETRIC * SURFACES .28 4.3 PRESSURE-DEPTH DATA ... 28 4.3.1 Theoretical Pressure-Depth Relationships . 28 4.3.2 Pressure-Depth Diagrams From Counties in Texas and Newlexico . .33 4.4 WOLFCAMP AND PENNSYLVANIAN PRESSURE-DEPTH DATA . .33 4.5 ABNORMAL FORMATION PRESSURES . .36 iii TABLE OF CONTENTS Page 1 EXECUTIVE SUMMARY ................... 1 2 INTRODUCTION ......................................... 5 .............. 2.1 PURPOSE AND SCOPE ............................... 5 .............. 2.2 METHODS, ASSUMPTIONS, AND LIMITATIONS ........... 6 .............. 2.3 SOURCES OF DATA ................................. 6 .............. 2.4 HYDROGEOLOGIC SETTING ........................... ............... 8 2.4.1 Regional Geologic Setting................. ............... 8 2.4.2 Hydrostratigraphic Units ................. ............... 11 2.5 PREVIOUS INVESTIGATIONS ......................... 16 .............. 2.6 COMPUTER PROGRAMS ............................... 17 .............. 2.6.1 SURFACE II GRAPHICS SYSTEM ............... 17 .............. 2.6.2 STATISTICAL ANALYSIS SYSTEM ............... 19 .............. 2.6.3 TRENDS ................................... 19 .............. 3 DRILL-STEM TEST CLASSIFICATION AND MASTER FILE . ........... 20 3.1 PURPOSE OF CLASSIFICATION SCHEME ............................... 20 3.2 CLASSIFICATION SCHEME ......................................... 20 3.3 CLASSIFICATION RESULTS ......................................... 23 3.4 MASTER FILE OF GEOLOGIC, HYDROLOGIC, AND FORMATION PRESSURE DATA .................................................. 23 4 WOLFCAMP AND PENNSYLVANIAN POTENTIOMETRIC SURFACES . 26 4.1 GENERAL ..................................................... 26 4.2 INITIAL WOLFCAMP AND PENNSYLVANIAN POTENTIOMETRIC SURFACES ..................................................... 28 4.3 PRESSURE-DEPTH DATA ........................................... 28 4.3.1 Theoretical Pressure-Depth Relationships ............... 28 4.3.2 Pressure-Depth Diagrams From Counties in Texas and New Mexico ................................. 33 4.4 WOLFCAMP AND PENNSYLVANIAN PRESSURE-DEPTH DATA . 33 4.5 ABNORMAL FORMATION PRESSURES ................ ................... 36 iv TABLE OF CONTENTS (Continued) Page 4.6 WOLFCAMP AND PENNSYLVANIAN POTENTIOMETRIC SURFACES AFTER CULLING DEPRESSURED DST DATA ............................. 37 4.6.1 Culling of Depressured DST Data ......................... 37 4.6.2 Wolfcamp and Pennsylvanian Potentiometric Surfaces After Culling Depressured DST Data ............. 46 4.7 WOLFCAMP AND PENNSYLVANIAN POTENTIOMETRIC SURFACES AFTER CULLING DEPRESSURED, GROSSLY UNDERPRESSURED, AND GROSSLY OVERPRESSURED DST DATA . 53 4.7.1 Culling of Grossly Underpressured and Grossly Overpressured DST Data ................................. 53 4.8 STATISTICAL ANALYSIS OF CULLING PROCEDURES . 62 4.9 SUMMARY AND INTERPRETATION OF POTENTIOMETRIC SURFACES ... 65 4.10 COMPARISON OF WOLFCANP AND PENNSYLVANIAN POTENTIOMETRIC SURFACES WITH PREVIOUSLY PUBLISHED POTENTIOMETRIC SURFACES .. 67 4.10.1 General Comparison of Methods ........................... 67 4.10.2 Specific Comparison of Methods and Results ............. 68 5 PRESSURE-DEPTH ANALYSES .. 71 5.1 HIGH PLAINS/ROLLING PLAINS PRESSURE-DEPTH RELATIONSHIP ......... 71 5.2 PLANAR REGRESSION OF WOLFCAMP AND PENNSYLVANIAN ISIP DATA ..................................................... 76 5.2.1 General ................................................. 76 5.2.2 Hypothetical Wolfcamp Plane ............................. 77 5.2.3 Hypothetical Pennsylvanian Planes ....................... 77 5.2.4 Conclusions and Geologic Implications ................... 81 6 SUMMARY AND CONCLUSIONS ............................................. 92 6.1 WOLFCAMP AND PENNSYLVANIAN POTENTIOMETRIC SURFACES . 92 6.1.1 General ................................................. 92 v TABLE OF CONTENTS (Continued) Page 6.1.2 Wolfcamp Potentiometric Surface ......................... 94 6.1.3 Pennsylvanian Potentiometric Surface ..................