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Abstract: High Resolution Aeromagnetic Evidence for
Deep Seated Structural and Fault Control on
Hydrocarbon Entrapment and New Oil and Gas
Targets – East Texas and Northwest Louisiana
The relationships between structurally and stratigraphically entrapped oil and gas fields and underlying magnetic basement along the southern margin of the East Texas basin and southern and eastern flanks of the Sabine Uplift in Louisiana have been evaluated by integrating a high resolution aeromagnetic survey with a comprehensive Lower Cretaceous subsurface geologic dataset. Well control and field studies confirm that structures and faults are instrumental in controlling reservoir entrapment. The location of fields in this system, along with production from a variety of Woodbine, Austin Chalk, and deeper reservoirs, bears a direct relationship to deep, wrench fault-related structures imposed on the basement during the Ouachita – Marathon Orogeny and re-activated during various episodes of readjustment throughout the development of the Gulf of Mexico.
The aeromagnetic survey entails 25,000 line-miles of high resolution aeromagnetic data that was flown with a half-mile by one-mile flight-line grid. Flight altitude was 500 feet above ground. Surveying utilized GPS navigation, digital diurnal monitoring, high sensitivity Cesium vapor magnetometer and video ground recording. Careful de-culturing, profile analysis and grid filtering produced impressive images of residual structural highs, basement faults, intrasedimentary faults and regional wrench faults. Color SUNMAG/AUTOFAULT and gray shade images highlight the structure and fault trends at selected “pseudo depth slices”. Detailed 2-D Werner and 3-D Euler depth estimation provide a series of fault picks at different depths in the section.
The subsurface dataset incorporates over 40 sequence stratigraphic picks, net porosity evaluations from over 1000 wells and core descriptions in eastern Texas and western Louisiana. Interrelationships were examined among oil and gas production, aeromagnetic fault and structural patterns and isopach and porosity patterns within Lower Cretaceous stratigraphic intervals. These suggest that paleostructural trends exerted a strong influence on deposition, reservoir development and hydrocarbon entrapment. These relationships also suggest that this approach can be utilized to define exploration lead areas in other stratigraphic, structural and fracture plays both shallower and deeper where subsurface control is sparse or non-existent. This integrated approach is shown to be a good, non-invasive exploration tool for prospecting in advance of leasing and 3D seismic shooting.
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