Date of Award
Master of Science - Geology
Dr. Wesley Brown
Dr. Chris Barker
Dr. R. LaRell Nielson
Dr. Walter L. Trikosko
Salt domes are important geological structures because they are potential major hydrocarbon traps and have a profound effect on overlying strata in the subsurface. Over five hundred salt domes have been located on the United States Gulf Coast region, including the Hastings Salt Dome. Hastings Oil Field is located about 40.2 km (25 miles) southeast of Houston, Texas. The Hasting oil field was discovered in 1934 and it was considered the largest oil reserve on the Gulf Coast. Its peak production of 75,000 BOPD (barrels of oil per day) was recorded in 1977 and it had a cumulative production of 582 MMBO (million barrels of Oil) as at February 2011.
Gravity surveying is a geophysical method of investigating subsurface features based on differences in rock densities. This is carried-out by using a gravimeter, which is an instrument that measures variations in gravitational attraction over the surface of the earth. Five hundred and thirty-seven gravity readings (including base station readings) were collected along roads and accessible routes in the study area by using a CG-5 Scintrex Autograv Gravimeter. Gravity readings were collected at every one-third to one-fourth of a mile. The CG-5 Autograv instrument measures relative gravity readings of the earth’s gravitational fields.
Geographical coordinates for each of the gravity station was determined with the aid of a Trimble NOMAD GPS unit. A Digital Elevation Model over the study area was generated from LiDAR data and this provided elevation values for each gravity stations. These elevation values were used for elevation corrections (free-air correction and Bouguer correction), which is an important aspect of gravity correction in creation of a Bouguer Anomaly map. Bouguer Anomaly reveals lateral variation in density of rocks at the subsurface. Two oval gravity low anomalies were found and interpreted as Hastings and Manvel Salt Domes. Data retrieved from the Texas Natural Resources Information System database revealed a series of normal faults within the area of the Hastings Salt Dome. Well log correlation, application of the concept of creekology, and a detailed gravity study accurately revealed the location and other physical characteristics of the Hastings Salt Dome. Well log correlation also revealed evidence of uplift of the overlying sedimentary beds over the Hastings Salt Dome. The flow pattern of the Clear Lake creek over Hastings Salt Dome supports the evidence of the presence of a subsurface feature. The Digital Elevation Model revealed surface imprints (isolated highs) associated with the presence of Blue Ridge, Pierce Junction and Webster salt domes but this was not observed over the Hastings Salt Dome.
This study will ultimately lead to a better understanding of the size, geometry, depth and structure of the Hastings Salt Dome.
Okocha, Francis C., "Gravitational Study of the Hastings Salt Dome and Associated Faults in Brazoria and Galveston Counties,Texas" (2017). Electronic Theses and Dissertations. 80.
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