Browsing by Subject "Petroleum -- Geology -- Texas -- Gulf Region"

Now showing 1 - 2 of 2

Facies architecture and production characteristics of strandplain reservoirs in the Frio Formation, Texas
(University of Texas at Austin. Bureau of Economic Geology, 1985) Tyler, Noel
Many modern shore zones comprise a continuum of depositional environments that encompass both strandplain and barrier-island systems. Strandplains are further subdivided into two classes: sand-rich beach-ridge plains and mud-rich chenier plains. Tertiary shorezone systems of the Texas Gulf Coast Basin contain a significant proportion of the Texas oil resource in clastic reservoirs. These reservoirs display better-than-average oil recovery efficiencies. This report describes the production attributes of three Frio strandplain reservoirs--the Cayce, the Cornelius, and the Carlson--in the North Markham-North Bay City field, Matagorda County, Texas.Hydrocarbons in the North Markham-North Bay City field were trapped in a simple rollover anticline. Oil is produced from stacked strandplain sandstones in this multiple reservoir field. Composite sandstones of beach-ridge plain/distributary/delta-front origin constitute the Cayce oil reservoir. Internal heterogeneity results in considerable fluid-flow anisotropy, as displayed by sequential water-cut maps and oil production maps. Water influx in the strandplain deposits follows broad fronts, whereas water invasion in channel deposits is more restricted and erratic. The Cornelius reservoir was deposited in a system intermediate between sand-rich beach plains and mud-rich chenier plains. Sandy beach ridges, separated by muddy swales, compose the productive framework of this class of strandplain reservoir and furthermore act as conduits for early water influx. Sandstones, possibly of washover origin, in the intervening swales produce oil but are more rapidly drained than are beach-ridge sandstones. The Carlson reservoir produces from transgressed strandplain deposits. Oil is contained in upward-fining transgressive sandstones that rest on thicker but oil-barren progradational facies. Facies analysis indicates that the Carlson had a complex and episodic depositional history, yet water-influx maps and oil production maps suggest isotropic fluid behavior. Modern sand-rich transgressive shore-zone deposits are characteristically sheetlike, as is the transgressive component of the Carlson reservoir. This distinctive morphology appears to have fostered reservoir productivity.Oil recovery from the North Markham-North Bay City reservoirs follows a predictable trend. Recovery efficiency is highest from the transgressive sheet sands of the Carlson, which is the shallowest of the major oil reservoirs; intermediate from the composite Cayce; and lowest from the depositionally complex and mud-rich Cornelius, which overlies the Cayce. Reservoir efficiency of the strandplain sandstones in the North Markham-North Bay City field exceeds that of barrier and back-barrier deposits productive elsewhere in the Frio Formation of the central Texas Gulf Coast.
Lower Miocene (Fleming) depositional episode of the Texas coastal plain and continental shelf : structural framework, facies, and hydrocarbon resources
(University of Texas at Austin. Bureau of Economic Geology, 1986) Galloway, William E.
The Fleming Group and its basinward equivalents constitute the stratigraphic record of one of the major Cenozoic depositional episodes of the northern Gulf Coast Basin. The depositional sequence representing the episode is bounded above by the Amphistegina B shale and below by the Anahuac shale. Initially, lower Miocene (Oakville) progradation advanced across the broad submerged shelf platform constructed during earlier Frio deposition. When outbuilding reached the Frio paleocontinental margin, the rate slowed as large-scale growth faulting created a narrow lower Miocene expansion zone. The later portion of the lower Miocene episode, generally equivalent to the Lagarto Formation, was characterized by long-term shoreline stability and retreat punctuated by local, temporary progradation.In South Texas, the lower Miocene depositional framework includes the Santa Cruz fluvial system and the North Padre delta system. The bed-load fluvial complex fed a wave-dominated delta, constructing a broadly convex deltaic headland across the foundered Frio Norias delta system. Extensive wave reworking and longshore transport of sand and mud nourished a broad barrier island/ lagoon and strandplain complex that extended along the central and much of the northeastern Texas coast. This well-known barrier/strandplain system was bounded updip by a coastal plain traversed by numerous, small, intrabasinal streams. Near the present Sabine River, westernmost deposits of a continental-scale mixed-load fluvial and equivalent delta system extend beneath the Texas Coastal Plain and shelf from the Miocene depocenter in Louisiana. Here, the early phase of lower Miocene progradation was also complicated by the incision and filling of numerous submarine gorges.Lower Miocene reservoirs have produced nearly 4 billion barrels of oil equivalent of petroleum from nine identified plays in the Texas Coastal Plain and shelf. The most prolific play, the Houston Embayment salt domes, accounts for nearly all the oil and more than two-thirds of the total production from deposits of the episode. Four offshore plays offer the greatest area for discovery of substantial new reserves, primarily of gas. To date, however, the yield per volume of reservoir sandstone for Miocene plays remains low relative to more prolific units, such as the Frio Formation.