Detection and Avoidance of Karst Related Shallow Geohazards Using Ultra High Resolution Full Tensor Gravity Gradiometry in the Delaware Basin, Texas

Abstract

Newly acquired Full Tensor Gravity Gradiometry (FTG) data identifies and maps shallow dissolution karst related geohazards over the Delaware Basin in Culbertson and Reeves Counties, Texas. The survey covers around 105 km² with surveying lines spaced every 100m. The project was commissioned after experiencing significant fluid loss after penetrating open voids within the Castille Formation in four recently drilled wells within the survey area. The main project goal is to identify caverns, systems of caverns or high-porosity brecciated zones related to dissolution karsting in which the open voids represent a significant drilling hazard, and to develop workflows to quantify drilling risk related to said features. The data reveals good correlation of expected anomaly patterns near the wells that experienced drilling fluid losses. Additional successful wells are compared to the data and new wells were drilled without experiencing significant drilling fluid losses. The data also compares to published data on mapped cavern systems and karst features outcropping in the Castille Formation immediately west of the survey area. The data reveals strong correlation to regional fault and fracture networks which are known to control hypogenic karst features mapped within the Castille Formation. High and low risk areas are identified to assist in future well pad selection. The survey cost is below the cost incurred by the drilling fluid losses with FTG data demonstrating its optimal efficiency in de-risking the area for shallow hazards.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018