Sub-salt Play Research Articles

Pore typing using nuclear magnetic resonance, an example with samples from cretaceous pre-salt lacustrine carbonates in the Santos Basin, Brazil

The Brazilian sub-salt play carbonate reservoirs present highly complex and heterogeneous pore systems, making it difficult to define their petrophysical properties, which is essential for the reservoir characterization. Nuclear magnetic resonance (NMR) has emerged as an effective tool in the petrophysical characterization of carbonates, both on the core and log scales. This work uses plug samples from the Barra Velha Formation in the Santos Basin, SE Brazil, which is characterized by unconventional lacustrine carbonate deposits dominated by shrub-like forms and spherulitic allochems. The porosity types were defined based on NMR laboratory analysis associated with petrographic descriptions and high-resolution X-ray computed tomography. From the NMR results it is possible to define irreducible water saturation and calculate porosity and permeability for each sample. The results obtained through the resonance technique showed high correlation with the porosity and permeability values obtained by gas injection. Additionally, the interpretation of the data enabled the division of samples into porous and tight categories and the definition of groups with characteristics of tight, good and excellent reservoirs. The interpreted data contributes to a better understanding of the petrophysical properties of these complex and heterogeneous samples.

Exploring the sub-salt play in the frontier Amadeus Basin - Insights from regional 2D seismic and potential field data

Early exploration of the frontier Amadeus Basin in the Northern Territory has been limited due to its size and remoteness, along with complexity of structuring and limited early success. The primary exploration targets of the southern Amadeus are the sub-salt and intra-salt plays of the Neoproterozoic lower Gillen-Heavitree petroleum system. Two wells have tested the sub-salt play, both flowing gas with high helium content, confirming the sealing capacity of the Gillen evaporates despite two significant orogenic events.In 2013, the first regional framework of 2D seismic was acquired over the southern Amadeus. In areas where seismic coverage is sparse, or of poor quality due to halotectonics, higher spatial density magnetic and gravity surveys have been used to interpolate trends between seismic and well control and create a high resolution depth-to-basement model. Alternate methods of seismic processing have also been trialled to improve sub-salt imaging.The newly acquired seismic and depth-to-basement model are revealing the architecture of the basin and provide a regional perspective of the sub-salt and intra-salt plays. With improved seismic imaging large sub-salt structures are emerging beneath the complex folds resulting from thin-skinned deformation.Learnings from the challenges associated with acquisition and processing, along with a better understanding of the complex halotectonics, will have significant implications for future exploration in the region.

地震波シミュレーションが地下構造探査に果たす役割

Seismic simulation technology has been developed for many years. Recent trend that targets of exploration have become deeper and more complicated recalls demand of the seismic simulation technology. However, it has been only used for limited study due to various technical reasons. In recent years, the seismic simulation technology is rapidly advanced with new simulation methods and parallel computers. We have developed the wave propagation methods and applied to various exploration problems. We will show some results of seismic simulation in this paper.The first example is related to the Marmousi model. This simulation result shows that the wave propagation is very complicated and is beyond our image. The second example is a virtual seismic survey related to the sub-salt play. The virtual exploration shows the problems and solutions for sub-salt seismic imaging. The third example is the difference between acoustic and elastic modeling. This result shows the problem in onshore seismic data and the future direction.Using a seismic simulation, we can recognize various pitfalls and limitation in seismic processing and seismic interpretation. Seismic simulation can be used as potential tools for virtual explorations. We can gain the knowledge and the virtual experience through the virtual explorations.

Abstract: The Relative Value of Geophysical Tools in the Gulf of Mexico Subsalt Play

Abstract: The Relative Value of Geophysical Tools in the Gulf of Mexico Subsalt Play

Subsalt Play, Gulf of Mexico: A Review

Exploration for deep-water sandstone reservoirs beneath allochthonous salt in the Gulf of Mexico represents a major new frontier play in North America. More than 30 wells thus far have been drilled with subsalt targets, resulting in 8 discoveries, at least 3 of which are commercial and 3 that have reserves of 100 million bbl oil equivalent or more. Reservoirs consist of Miocene-Pleistocene sandstones deposited in submarine fan channel system environments on the paleoslope, where salt deformation has a complex late Cenozoic history. Salt sheets exist at various stratigraphic levels and have overridden sandstone fairways on the present-day outer continental shelf and upper slope, where water depths are moderate and where pipeline and other infrastructure facilities already exist. Potential reserves for the subsalt play have been estimated at 1.2 billion bbl of oil and 15 Tcf* gas from 25 or more significant fields. Recent success in the subsalt play has depended upon (1) advances in 3-D (three-dimensional) seismic acquisition and processing (in particular, 3-D prestack depth imaging) and (2) improved geologic modeling of salt deformation and depositional systems. In addition, better understanding of the drilling risks frequently encountered in penetrating salt sheets has been important. Progress in all these areas ismore » certain to continue and will result in significant new tools and techniques for exploration as a whole.« less

The Evolving Exploration of the Subsalt Play in the Offshore Gulf of Mexico: ABSTRACT

The Evolving Exploration of the Subsalt Play in the Offshore Gulf of Mexico: ABSTRACT

Origin and Early Development of the Gulf of Mexico Basin Based on 15-Second Record Seismic in the Louisiana Shelf and Upper Slope: ABSTRACT

A 4x4 mile grid of new 15-second record seismic data covering the entire Louisiana shelf and upper slope reveals new insights into the deep structure of the Gulf of Mexico Basin. Noteworthy is the absence of evidence for major horst and graben basement faulting predicted in some models for the early Gulf under the shelf. Instead, the basement appears generally smooth, with a reasonably conformable early section 1 to 1.5 seconds thick immediately overlying it. This suggests either that the basement was formed as lower plate continental crust (in a simple shear detachment fault scenario, below the brittle-ductile crustal transition) or as oceanic crust similar to that observed under autochthonous salt in the Perdido fold belt. If the latter is correct, the edge of oceanic crust needed to reconstruct the sea-floor spreading history may nearly coincide with the current northern limit of the sub-salt hydrocarbon play, possibly because the play location depends on 3-4 km thick salt originally deposited in the area under the southern shelf. The southern limit of thick LouAnn salt is related to depositional factors (evaporation, oceanic circulation, etc.) rather than to underlying crustal type. An unresolved question is the nature of the section overlying the smoothmore » basement event. Both deepwater Lower Cretaceous (chalks, marts ?) and Eagle Mills deepwater equivalents (shales) are plausible interpretations.« less

Gas Exploration and Development in the Gulf of Mexico: A Totally Integrated Approach to Profitability: ABSTRACT

Operators in the prolific offshore Gulf of Mexico increasingly capitalize on technology and multidsciplinary teamwork to deliver significant new gas reserves. Gas opportunities range from extensions in mature fields and exploration discoveries on the shelf to significant new volumes in deepwater. In addition, recent discoveries in the sub-salt play are encouraging for the future gas potential in the Gulf of Mexico basin. The recent resurgence in Gulf of Mexico drilling and development activity is driven by a relatively strong market for natural gas, coupled with technical factors that contribute to improving success ratios and overall project profitability through a well-integrated approach to exploring, developing, and exploiting gas reserves. Regardless of the size of the volume opportunities, the critical success factor is reduction of risk and uncertainty through development of an accurate interpretation of the subsurface. 3-D seismic integrated with well data, geologic models, amplitude analysis (including AVO), and reservoir modeling are routinely used to develop high rate well locations. Deepwater projects also focus on reservoir architecture prediction to optimally space the high ultimate volume wells necessary to justify these higher development costs. These efforts are typically accomplished by multidiscipline teams of geoscientists and engineers working closely to optimize projects for more » enhanced profitability. This integrated approach has been enabled through process re-engineering and organizational changes that have significantly improved overall cost structures and project cycle times. Case examples clearly demonstrate how integrated technical and operational approaches can lead to exceptional results from the nature Shelf and the frontier Deepwater areas of the Gulf of Mexico. « less

The Evolving Exploration of the Sub-Salt Play in the Offshore Gulf of Mexico: ABSTRACT

The Evolving Exploration of the Sub-Salt Play in the Offshore Gulf of Mexico: ABSTRACT