Khaled Fouad

Traps and turbidite reservoir characteristics from a complex and evolving tectonic setting, Veracruz Basin, southeastern Mexico

The Miocene and Pliocene interval of the Veracruz Basin, southeast Mexico, experienced an evolving array of shortening, strike-slip, and volcanic forces in response to plate-scale interactions. The basin is divided into six structural domains that define regions of comparable timing and type of structural deformation, and the basin fill is separated into two long-term depositional phases, each of which can be tied to a waning and then waxing of major basin-bounding tectonic events. The first phase of deposition took place from the early to late Miocene and is tied to the waning effects of the Laramide orogeny. The Miocene basin inherited a tectonically steepened basin margin, across which deep canyons were carved and variably filled with mudstone and thin remnants of coarse sandstone and conglomerate. This zone of erosion and bypass grades into thick, sandstone-rich basin-floor fans. Later in phase I, subaqueous volcanoes, tied to distant plate subduction, developed offshore and formed a bathymetric barrier that prevented turbidity currents from entering the ancestral Gulf of Mexico. The volcanoes also served as immovable buttresses, around which intrabasinal thrust belts developed in response to regional shortening.The second depositional phase is tied to the onset of internal basin shortening and uplift of the north basin margin known as the trans-Mexican volcanic belt. This uplift caused a dramatic reconfiguration of the sediment-dispersal system, whereby large shelf clinoforms prograded from north to south across the basin. In contrast to the onlapping stacking pattern of phase I units, phase II units stack in a strongly offlapping pattern.Proven and postulated reservoir-trap combinations, ranging from four-way to three-way combination (stratigraphic), to pure stratigraphic traps are common. Four-way closures mapped from the two-dimensional and three-dimensional seismic data are large (P50: 5000 km2) and are covered with thick, lower Miocene fan sandstones. Traps that depend on a stratigraphic component are thinner and smaller in size (P50: 1000 km2), but more numerous than the four-way closures. Because many structures have experienced prolonged pulses of compression, top seal is considered an important geologic risk to the retention of substantial gas-column heights.

A multistep approach to multicomponent seismic image registration with application to a West Texas carbonate reservoir study

Application of multicomponent seismic exploration produces multiple images of the same subsurface. For a successful interpretation of multicomponent images, it is crucially important to register them in the same coordinate frame. Accurate registration of time-domain images also provides an effective estimate of the interval VP/VS ratio, a major petrophysical attribute. We propose a multistep approach to image registration, which consists of initial interpretation, amplitude and frequency balancing, registration scan, and least-squares optimization. The approach is applied successfully to a 3C3D seismic dataset from West Texas, where multicomponent image registration provides an insight into a targeted carbonate reservoir facies.

Neogene tectonic, stratigraphic, and play framework of the southern Laguna Madre–Tuxpan continental shelf, Gulf of Mexico

Neogene shelf, slope, canyon, and slope-to-basin-floor transition plays in the southern Laguna Madre–Tuxpan (LM-T) continental shelf reflect a variety of structural and stratigraphic controls, including gravity sliding and extension, compression, salt evacuation, and lowstand canyon and fan systems. The Neogene in the LM-T area was deposited along narrow shelves associated with a tectonically active coast affected by significant uplift and erosion of carbonate and volcanic terrains. This study characterizes 4 structurally defined trends and 32 Neogene plays in a more than 50,000-km2 (19,300-mi2) area linking the Veracruz and Burgos basins. The Caonero trend in the southern part of the LM-T area contains deep-seated basement faults caused by Laramide compression. Many of these faults are directly linked to the interpreted Mesozoic source rocks, providing potential pathways for vertically migrating hydrocarbons. In contrast, the Lankahuasa trend, north of the Caonero trend, contains listric faults, which detach into a shallow horizon. This trend is associated with thick Pliocene shelf depocenters. The dominant plays in the Faja de Oro–Nyade trend in the central part of the LM-T area contain thick lower and middle Miocene successions of steeply dipping slope deposits, reflecting significant uplift and erosion of the carbonate Tuxpan platform. These slope plays consist of narrow channel-fill and levee sandstones encased in siltstones and mudstones. Plays in the north end of the LM-T area, in the southern part of the Burgos basin, contain intensely deformed strata linked to salt and shale diapirism. Outer-shelf, slope, and proximal basin-floor plays in the Lamprea trend are internally complex and contain muddy debris-flow and slump deposits. Risk factors and the relative importance of play elements vary greatly among LM-T plays. Reservoir quality is a critical limiting play element in many plays, especially those in the Caonero trend directly downdip from the trans-Mexican volcanic belt, as well as carbonate-rich slope plays adjacent to the Tuxpan platform. In contrast, trap and source are low-risk play elements in the LM-T area because of the abundance of large three-way and four-way closures and the widespread distribution of organic-rich Upper Jurassic Tithonian-age source rock. The potential for hydrocarbon migration in LM-T plays is a function of the distribution of deep-seated faults inferred to intersect the primary Mesozoic source. Their distribution is problematic for the Lankahuasa trend, where listric faults sole out into the Paleocene. Seal is poorly documented for LM-T plays, although the presence of overpressured zones and thick bathyal shales is favorable for seal development in middle and lower Miocene basin and slope plays.

Geologic framework of upper Miocene and Pliocene gas plays of the Macuspana Basin, southeastern Mexico

This integrated study provides a geological and geochemical framework for upper Miocene and Pliocene siliciclastic gas plays in the Macuspana Basin. Structural controls for the plays are deep-seated faults that tap Mesozoic thermogenic gas sources, areas of intense shale diapirism and folding, and areas with structural inversion that could enhance trapping and reservoir productivity. Early Neogene thrusting south of the basin triggered evacuation of Oligocene shale along northwest-dipping listric faults in the eastern and southeastern basin margin. These faults are associated with large-scale rollover structures and thick (500 m) upper Miocene shoreface and wave-dominated deltaic complexes. A second phase of extension in the early Pliocene formed a set of broad, southeast-dipping listric faults in the western basin, controlling thick accumulations of stacked Pliocene shoreface deposits. Trap formation and enhancement in the southern basin margin are linked to late Miocene to Pliocene inversion.The primary stratigraphic controls on play occurrence in the upper Miocene in the onshore part of the basin are the regional facies distribution of northwest-prograding shoreface and wave-dominated deltaic systems. There was a shift in Pliocene sedimentation from the southeast to the west and northwest parts of the basin, where thick successions of aggradational shoreface and wave-dominated deltaic deposits accumulated in depocenters defined by shale evacuation along growth faults. Valley-fill deposits in both the upper Miocene and Pliocene resulted from shortlived periods of base-level change induced by either uplift on the southern basin margin or eustasy. The offshore part of the basin is inferred to consist of deep-water turbidite deposits that formed downdip (westward) of a hypothesized mixed clastic-carbonate prograding complex from the Yucatan platform.Three petroleum systems (Mesozoic, Paleogene–lower Neogene, and upper Miocene–Pliocene) contributed to the hydrocarbon accumulations and hydrocarbon generation and migration in the basin. Principal Upper Jurassic/Lower Cretaceous source rocks generated wet thermogenic gases and oil. Secondary lower Tertiary source rocks generated dominantly dry biogenic gases. Mixtures of the two gas types are common. Numerous deep-seated growth faults and faults serve as pathways for Mesozoic-sourced hydrocarbons. Surface seeps and abundant gas shows suggest that hydrocarbons are being generated today.

Multicomponent seismic technology for imaging deep gas prospects

Across the Gulf of Mexico, operators are targeting deeper and deeper drilling objectives. For deep targets to be evaluated, seismic data require relatively long source-receiver offsets. Most shallow-water operators in the gulf consider 30 000 ft (9 km) to be the deepest target depth that will be drilled for the next several years. For geology at depths of 9 km to be imaged, seismic reflection data must be acquired with offsets of at least 9 km. We suggest in this paper that modern 4-C OBC data can provide good quality P-SV data to such depths and should be integrated into prospect evaluations. Long-offset surveys are difficult to achieve using towed-cable seismic technology in areas congested with production facilities, typical for many shallow-water blocks across the northern Gulf of Mexico shelf. Ocean-bottom-cable (OBC) and ocean-bottom-sensor (OBS) technologies are logical options for long-offset data acquisition in congested production ar-eas because ocean-floor sensors are immobile once deployed and can be positioned quite close to platforms, well heads, or other obstructions that interfere with towed-cable operations. An example illustrating the deployment of ocean-floor sensors through a congested platform complex in part of the area of study is illustrated in Figure 1. A 10-km diameter circle is positioned atop this map of production facilities to illustrate the difficulty of towing a 10-km cable across the area in any azimuth direction. In contrast, OBC lines AA, BB, and CC (actual profiles used in this study) pass within a few meters of several production platforms. Figure 1. 4-C OBC data acquisition across congested areas. An additional appeal of OBC seismic technology is that 4-C data can be acquired, allowing targeted reservoir intervals to be imaged with P-SV wavefields, as well as P-P wavefields. Once 4-C seafloor receivers are deployed, source boats can maneuver along a receiver line to …

Characterization of reservoirs in the Tertiary section of Block B in the south of Lake Maracaibo

Substantial hydrocarbon resources reside in stratigraphically and structurally complex Tertiary reservoirs in South Lake Maracaibo, but in Block B (Figure 1), production to date has amounted to little more than 70 000 barrels. This poor production performance motivated Lagoven SA, an affiliate of Petroleos de Venezuela SA, to initiate a joint contract with the Bureau of Economic Geology to investigate the reservoir characteristics and ultimately to produce commercially the hydrocarbons in place. The primary objectives of the study were (1) to identify the remaining oil reserves in the Tertiary reservoirs of Block B through integrated geologic, geophysical, and engineering analysis and (2) to develop drilling and completion strategies to exploit the existing reserves. To understand the fundamental characteristics of the reservoir and design a development program that incorporates the inherent reservoir heterogeneity, the Bureau applied a four‐step procedure: (1) determine geologic reservoir architecture wi...

Genetic Facies Analysis Using Seismic Geomorphology and Seismic Attributes in the Continental Shelf of Eastern Mexico

Methods for generating seismic facies maps have developed significantly in the last decade. These methods include facies mapping based on seismic geomorphology and sequence attribute extractions (Posamentier and Kolla, 2003). The results of these methods are used to define depositional systems, erosion, paleotopography, and inferred lithology estimation.The seismic geomorphology technique is similar to back-stripping of a geologic sequence that represents a certain time-stratigraphic surface. We analyze depositional features from timeslices and windowed attribute extractions in a flattened volume within a stratigraphic sequence. Facies can be inferred from the resulting interpreted maps, which basically confine the variation in seismic reflections. Such variation, caused by geology change within seismic sequences and systems tracts, is expressed by change in reflection pattern, amplitude, and frequency (i.e., chaotic, hummocky, continuous). This technique produces quick and efficient results that capture the lateral changes in reflection pattern geometries.In this article, we demonstrate how we deployed seismic geomorphology and attribute extraction to build out the facies in a third-order sequence. We show an example in the Laguna Madre area, a 3-D cube that extends over 2000 km2 southeast of the Tuxpan Platform. This research is part of a study done by the Bureau of Economic Geology to investigate Neogene hydrocarbon plays in the Tuxpan area.

Wave-shape classification and attribute analysis of the lower Miocene deep-water reservoirs, Laguna Madre Basin, offshore México

The lower Miocene deep-water play in Laguna Madre Basin contains attractive depositional features and yet is considered high-risk potential. Previous economic activity within this region largely focused on large traps within carbonate rocks of the Tuxpan Platform. Recently interest has renewed in exploring natural gas reserves in the Neogene plays. In this study, we analyzed a nonproductive horizon representing the base of the Miocene and containing an apparent toe-of-slope channel complex in the proximal part of the basin.

Seismic Facies And Attribute Analysis of the Miocene Incised-valley-fill And Submarine-canyon Systems In Tuxpan Basin, Offshore México

In this study, we demonstrate the seismic facies and attribute analysis in upper Miocene incised-valley-fill and submarine-canyon systems in the Laguna Madre-Tuxpan area north of Veracruz. Following initial structural identification by PEMEX geoscientists, seismic imaging techniques were used to build a stratigraphic model on the basis of seismic sequence and attribute analysis. Seismic wave-shape analysis using neural-network wavelet classification was employed to describe the canyon-fill deposits. These techniques were applied in the imaging of lower-canyon-fill successions that are inferred to be sandstone-rich where they onlap onto faulted submarinecanyon margins. In contrast, overlying upper-canyon-fill deposits from progradational highstand delta-front deposits consist of thin delta-front sandstones intercalated with distal prodeltaic siltstones and are genetically associated with a fine-grained succession providing a shaly drape over the sandy lower-canyon-fill.

Seismic imaging of upper Miocene fluvial reservoirs in the southern Macuspana Basin, Southeastern México

Major gas reservoirs in the south part of the Macuspana Basin occur in upper Miocene fluvial and wave-dominated deltaic deposits. A recent joint study by the Bureau of Economic Geology and PEMEX Exploracion y Produccion defined the depositional systems and reservoir styles of the Tertiary section in the basin. Seismic data were integrated with log and production data to delineate sandstone architecture, reservoir limits, and hydrocarbon occurrence. Sandstone geometries were imaged using conventional interval and windowed attribute extraction techniques. A strong decreasing impedance relationship and gas occurrence from different stratigraphic intervals was established from well logs. Although numerous direct hydrocarbon indicators (DHIs) were delineated and mapped from several stratigraphic units, future success was deemed to be dependent on identifying anomalies that represent high gas saturation. AVO modeling of reservoir sandstones was utilized to discriminate between brine, low and high gas saturation from seismic. This analysis of seismically bright amplitudes indicates that a wide range of gas saturation may be the cause of the anomalies. The results of this technique can significantly aid future exploration and development efforts.