Structural Evolution and Hydrocarbon Trapping Mechanisms: Hankamer Field Area, Liberty and Chambers Counties, Texas

Kathleen E. Herrington Mabe

The Hankamer field area, located in the Houston salt dome embayment, is associated with a deep-seated salt structure, and related complex graben and radial fault systems. Palinspastic restorations, geochemical and paleontological studies, and paleobathymetric maps have been used to reveal the structural evolution of the upper Eocene through middle Miocene sediments.

Data from 400 wells and 37 mi (60 km) of two-dimensional seismic data were integrated to generate structure, isopach, fault plane maps, and cross sections over a 74 mi² (192 km²) area. The palinspastic restoration of a seismic profile was constrained by maintaining the bed length and the volume of salt in two dimensions, and accounting for the depositional environment and water depth, established from a paleontological study. The palinspastic restoration provided insight into the structural configuration of the salt dome during late Eocene through middle Miocene and the timing of various faulting episodes.

The beginning stages of salt movement occurred on the upthrown side of a major counter-regional normal fault. Salt withdrawal created a rim syncline on the west flank of the field, indicated by a paleobathymetric low and isopach thick. A combination of lateral and upward salt movement caused additional counter-regional faulting along the west-northwest salt face, which is believed to have formed a pathway hydrocarbon migration from a deeply buried source bed. Salt movement contemporaneous with late Eocene through early Oligocene deposition resulted in a paleobathymetric high as evidenced by thinning and non-deposition or erosion over the salt crest. During the early through late Oligocene, salt movement on the east flank of the field caused an additional 600 ft (183 m) of vertical dis lacement on a radial normal fault, transversely oriented to the counter-regional fault system. This movement was indicated by an area of thinning and nondeposition or erosion of lower and upper Oligocene sediments on the upthrown side of the radial fault. A complex graben fault system developed parallel with this radial fault.

The combination of graben faulting and structural closure traps the majority of the oil in Hankamer field within Miocene sands. The palinspastic restoration and geochemical study suggest substantial late fault movement caused hydrocarbon leakage from the Oligocene into the Miocene sands.

This study demonstrates that a field established in 1929 with a cumulative production of 52 million bbl of oil can be more accurately mapped and developed by obtaining a better understanding of the field's structural evolution, migration history, and trapping mechanisms. As a result, additional development and delineation prospects have been defined in areas previously thought to be void of economic reserves.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.