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Selim S Shaker - One of the best experts on this subject based on the ideXlab platform.
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abstract integrated stratigraphic Geopressure fairway trends a fast track to boost success in semi mature basins a case history from the gulf of mexico
2006Co-Authors: Selim S ShakerAbstract:Abstract The new concept of integrating stratigraphy and Geopressure compartmentalization is a comprehensive risk assessment method and a fast track to success when used in semi-mature basins, where infrastructure is abundant. Stratigraphy, including depositional environment, impacts the spatial distribution of sand (reservoirs) and shale (seals). The optimum depositional environment for hydrocarbon trapping, especially in faulted structural closures, lies in the transition zone between the middle and outer shelf. In this zone, the sand to shale ratio is conducive to sealing of juxtaposed fault surfaces. Geopressure differential plays a principle role in determining migration of hydrocarbons from deeper source rocks and carrier beds to the shallower ones. The subsurface pressure profile is usually divided into two main zones, namely the lower Geopressured and the upper hydrostatic. The transition zone between the two zones is the major recipient of upward migrating hydrocarbons. In semi-mature basins such as the Gulf of Mexico, well logs and paleontological, production, drilling and test data can be integrated in a data base. The High Island - Galveston areas were used for a pilot study to test this concept. Stratigraphy and Geopressure trends were mapped for the different lower-middle Miocene units. Producing, potential pay and reservoirs trends were found to be clearly following the most favorable trends, where depositional environment and Geopressure gradient result in favorable reservoir characteristics and effective seals. This new method confirms the belief that 70% of hydrocarbons accessible without trouble are perched around the Geopressure transition zone. Therefore, risk of future prospective endeavors can be substantially reduced by tracking the optimum strat-Geopressure fairways.
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Geopressure progression regression an effective risk assessment tool in gulf of mexico deep water
2002Co-Authors: Selim S ShakerAbstract:ABSTRACT In the Tertiary-Pleistocene clastic sediments, compaction disequilibrium is the primary cause of Geopressure compartmentalization in the deep water of the Gulf of Mexico. A sealed compartment is the key for exploration success in any play concept. Estimating the shift of pore pressure envelopes in relation to Geopressure compartmentalization is essential in predicting objectives risk. The actual pressure measurements (i.e., RFT's and MDT's) in reservoir type sections show a cascade profile with depth in the Geopressured (abnormal) column. The amount of shift in the pressure envelopes designates the sealing and retention capacities. A correlation was found between the progressive-regressive shift and exploration success in some of these deep water wildcats. Substantial hydrocarbon accumulations were found where a considerable progressive shift was recorded (> 1000 psi), i.e., Green Canyon 809 #1, 72 # A-1, 506 #1, Mississippi Canyon 211# 1, and Viosca Knoll 1001#1. Marginal reserves or wet reservoirs were found where a small shift (< 1000 psi) was noticed, i.e., Garden Banks 543 #1, 142 #1; Green Canyon 908#2; and Keathley Canyon 255#1. On the other hand, where pressure envelopes show regressive behavior, the target reservoirs were unsuccessful, i.e., Garden Banks 248 #1 and Viosca Knolls 912#1. Bore-hole trajectory in relation to the Geopressure profile of each objective should be investigated before making a conclusive risk assessment. Study of this correlation on a basin to basin basis is imperative for the productive evaluation of seal integrity, compartments communication and potential hydrocarbon trapping. Concepts and Methods Pore pressure (PP) is the product of interaction between fluid and rock matrix due to compaction. Compaction is caused primarily by the weight of the deposits (overburden) coinciding with basin subsiding. An increase of principal stress with depth due to sedimentation load accelerates Geopressure. Pressure progresses with depth in a cascade fashion (Fig. 1) in a tectonically relaxed system (Shaker, 2001). Seal failure and upward communication are the main cause of pressure regression (Fig. 2). The measured actual pressure values, such as Repeat Formation Tester (RFT) and Modular Dynamics Tester (MDT), establish the progress and regress in the pressure envelopes. The sandwiching of seals between successive reservoir compartments (where PP is measured) is responsible for the very slow pressure decay in the entire subsurface section. Principal stress, pressure decay rate, and structural and stratigraphic settings are the driving mechanism behind progression and regression shifts in the subsurface. Progression System Shale beds negligible permeability and geological age lead to an immeasurable decay process in the progressive system. The PP decay in the progression system is usually very slow. This is due to the fact that the initial sealing capacity of the Geopressure compartmentalizations is still intact and follows the compaction disequilibrium laws as long as sedimentation and subsiding are in progress. This leads to relatively large envelopes. The success of finding commercial hydrocarbon accumulation depends on the size of this pressure envelope and its immediacy to the fracture limit. End_Page 893------------------------ Figure 1. Schematic Geopressure profile shows pressure envelopes progression with depth. The PP in the reservoir follows a linear hydrostatic gradient in the reservoir. On the other hand, predicted PP in the seal has a higher exponential gradient. The difference between pressure envelopes represents progression shift. Figure 2. Schematic Geopressure profile explains the most likely reason for pressure envelopes regression in the Gulf of Mexico. Upward communication is represented by dashed pathway at the right of the figure. PPP represents predicted pore pressure, and MPP represents measured pore pressure. End_Page 894------------------------ Regression System PP regression exists in cases where seals fail and upward communication through faults, salt walls, and facies interface takes place (Fig. 3). The PP decay in the regression system is relatively high due to the presence of large negative pressure difference between the seal and the underlying compartment (Fig. 4). The measured pore pressure in deeper reservoirs retreats to the same pore pressure gradient envelope as that of the shallow ones. Figure 3. A conceptional geological cross section on a salt ramp explains PP progression and regression. Progression takes place where the system is sealed. Regression exists where communication between the deep reservoirs and shallow ones takes place. Figure 4. Schematic Geopressure profile exhibits the pressure decay process in a regressed system over time throughout the seal. End_Page 895------------------------ Gulf of Mexico Cases Hydrocarbon accumulation in the subsurface of Geopressured structural and stratigraphic traps relies mainly on the seal integrity. The shift in the Geopressure envelopes indicates the capability of the seal (cap) to exert a certain pressure inside the compartment. Hydrocarbon presence in the reservoir inflates the virgin pressure in the reservoir beds. The introduced pressure, due to the presence of oil and gas, is proportional to the density and height of the hydrocarbon column. A direct relationship was found between the shift direction, as progressive or regressive, and the presence of oil and gas in the objective targets. Moreover, the size of the progressive shift impacts the size of oil and gas accumulations. Large Progressive Shift Most of the commercially discovered fields in the deep water of the Gulf of Mexico are characterized by large progressive Geopressure shifts. This shift takes place at the interface between the cap shale seal and the targeted reservoir compartment. Popeye (Green Canyon 72 # A-1), Fuji (Green Canyon 506 #1), Mickey (Mississippi Canyon 211#1), Ursa (Mississippi Canyon 809 # 1) and South Rampowell (Viosca Knoll 1001#1) fields show shifts usually exceeding 1000 psi (Fig. 5). Figure 5. Pressure-depth (P-D) plot of Mississippi Canyon Block 809 Well#1 shows the large progressive pressure envelopes coinciding with the presence of oil and gas in Ursa field. The GOM line on the left graph represents the regional Gulf of Mexico hydrostatic gradient. Pressure progressions are represented by the red arrows. Oil and gas pressure gradients are shown as green dashed and red dotted lines, respectively. Notice gas reservoir needs larger sealing capacity (progressive shift) than oil. End_Page 896------------------------ Small Progressive Shift Most of the economically marginal finds and unsuccessful wildcats are characterized by a small progressive shift (<1000 psi). Pressure decay rate, fracture gradient acceleration, and structural failure contribute to the weak progression shift. The plugged and abandoned wildcats drilled in Garden Banks 543 #1, Garden Banks 142 #1, and Green Canyon 908 #2; and Keathley Canyon 255#1 support this relationship (Fig. 6). Regression Pore pressure regression in the subsurface can be caused by several structural settings and stratigraphic events. Faults and salt walls act as fluid conduits from highly pressured deep compartments to lower pressured shallow ones. This leads to a pressure regression in the lower reservoirs (compartments). Consequently, in the deep compartment the pore pressure retreats to an envelope equal to the pressure in shallow reservoirs. The basal part of the Garden Banks 248#1 (Fig. 7) and Mississippi Canyon 211 #1 shows this pressure regression phenomenon. In this case the target objectives were barren of hydrocarbons. Titan Prospect (GB 785 # 1) tested a measured PP in the target reservoir of 1.8 ppgMWE less than the predicted surrounding shale (12.4 vs.14.2 ppgMWE) at depth 18500 ft. The well was plugged and abandoned (Dry Hole Seminar, 2000). Figure 6. P-D plot of Garden Banks 543 #1 shows the small progressive shifts (red arrows). Note the section between 11000 ft and 15000 ft has the same pressure envelope. This suggests that the stratigraphic column at this interval is in communication and trapping integrity is of high risk. The well was plugged and abandoned. End_Page 897------------------------ Conclusions Integrating the Geopressure compartmentalization data to the prospect geological model is essential for trapping and risk assessments. Sealed compartments usually are represented by a progressive Geopressure shift. The size of this shift reflects the capability of the cap rock to exert the introduced pressure by emplacing hydrocarbon in the reservoir. On the other hand, pressure regression indicates a seal failure and the incapability of the reservoirs to retain oil and gas. Therefore, bore-hole trajectory needs to be assessed in relation to compartmentalization in the prospective basin in order to evaluate trap integrity in each exploration target.
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Geopressure compartmentalization in keathley canyon deep water gulf of mexico
AAPG Bulletin, 2001Co-Authors: Selim S ShakerAbstract:ABSTRACT In the Gulf of Mexico, several salt related basins have attracted exploration. Keathley Canyon Block 255 Well #1 (TD 21550) has tested one of these basins. Extensive geological and Repeated Formation Tester data were collected from this well. Integration of the Geopressure profile and the structural setting demonstrates two distinctive main compartments. A hydrodynamically active compartment exists between the sea floor and the Hyalinea balthica upper Pleistocene shale section. This phenomenon may be responsible for the drilling problems and shallow water flow in this and similar relatively young basins. Therefore, entrapment of commercial volumes of hydrocarbon in this upper section is unlikely. A hydrostatically Geopressured main compartment extends between the upper effective seal of Hyalinea balthica to the Pliocene section at the bottom of the basin. This Geopressured thick section shows a progressive pressure profile with depth and can be divided into five mini-compartments (C1, C2, C3, C4, & C5). Four of these mini-compartments show effective seals (S1, S2, S4 & S5). On the other hand, on both sides of the incompetent seal (S3), the pore-pressure gradient remains in the same hydrostatic envelope. This also exhibits communication between C2 and C3 and indicates exploration targets in the C3 are high risk. Seals and reservoir lithology have a direct impact on the Geopressure profile progression with depth. On the other hand, the structural setting is responsible for pore pressure differential between the seal and reservoir (centroid concept). Drilling on the crest of high relief closure can be a challenging task in deep water exploration.
A.i. Opara - One of the best experts on this subject based on the ideXlab platform.
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Geopressure and Trap Integrity Predictions from 3-D Seismic Data: Case Study of the Greater Ughelli Depobelt, Niger Delta
Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles, 2012Co-Authors: A.i. Opara, K.m. Onuoha, C. Anowai, R.o. MbahAbstract:The deep drilling campaign in the Niger Delta has demonstrated the need for a detailed Geopressure and trap integrity (drilling margin) analysis as an integral and required step in prospect appraisal. Pre-drill pore pressure prediction from 3-D seismic data was carried out in the Greater Ughelli depobelt, Niger Delta basin to predict subsurface pressure regimes and further applied in the determination of hydrocarbon column height, reservoir continuity, fault seal and trap integrity. Results revealed that Geopressured sedimentary formations are common within the more prolific deeper hydrocarbon reserves in the Niger Delta basin. The depth to top of mild Geopressure ( 0.60 psi/ft) ranges from about 10 000 ftss to over 30 000 ftss. The distribution of Geopressures shows a well defined trend with depth to top of Geopressures increasing towards the central part of the basin. This variation in the depth of top of Geopressures in the area is believed to be related to faulting and shale diapirism, with top of Geopressures becoming shallow with shale diapirism and deep with sedimentation. Post-depositional faulting is believed to have controlled the configuration of the Geopressure surface and has played later roles in modifying the present day depth to top of Geopressures. In general, Geopressure in this area is often associated with simple rollover structures bounded by growth faults, especially at the hanging walls, while hydrostatic pressures were observed in areas with k-faults and collapsed crested structures.
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ORIGIN AND GENERATION MECHANISMS OF GeopressureS IN SHALE DOMINATED SETTINGS WORLD-WIDE: A REVIEW.
Global Journal of Pure and Applied Sciences, 2010Co-Authors: A.i. OparaAbstract:Geopressures are common in young Tertiary sedimentary basins where marine units underlie rocks of higher permeability. A low permeability environment and conditions that reduce available pore space or increase fluid volume are necessary for Geopressures to occur and be maintained. In the Niger Delta, Gulf of Mexico, and indeed worldwide, the generation of Geopressure is often related to the sedimentation rate, while its dissipation depends on the hydrological properties of the sediments(that is porosity, permeability, etc).Geopressures influences many fluid related aspects of petroleum geology including diagenesis, migration and accumulation of oil and gas ,and indeed reservoir quality. It also constitutes a hazard in drilling wells and directly impacts on drilling costs and the safety of petroleum exploration. The general overview of the different casual mechanisms and their relative contributions to the present day Geopressure regime is indeed very important. The objective of this work is therefore to review the different mechanisms of Geopressure and to assess the relative contributions of individual mechanisms to Geopressure development. A primary objective here is to critically evaluate the relative importance of each.
R.o. Mbah - One of the best experts on this subject based on the ideXlab platform.
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Geopressure and Trap Integrity Predictions from 3-D Seismic Data: Case Study of the Greater Ughelli Depobelt, Niger Delta
Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles, 2012Co-Authors: A.i. Opara, K.m. Onuoha, C. Anowai, R.o. MbahAbstract:The deep drilling campaign in the Niger Delta has demonstrated the need for a detailed Geopressure and trap integrity (drilling margin) analysis as an integral and required step in prospect appraisal. Pre-drill pore pressure prediction from 3-D seismic data was carried out in the Greater Ughelli depobelt, Niger Delta basin to predict subsurface pressure regimes and further applied in the determination of hydrocarbon column height, reservoir continuity, fault seal and trap integrity. Results revealed that Geopressured sedimentary formations are common within the more prolific deeper hydrocarbon reserves in the Niger Delta basin. The depth to top of mild Geopressure ( 0.60 psi/ft) ranges from about 10 000 ftss to over 30 000 ftss. The distribution of Geopressures shows a well defined trend with depth to top of Geopressures increasing towards the central part of the basin. This variation in the depth of top of Geopressures in the area is believed to be related to faulting and shale diapirism, with top of Geopressures becoming shallow with shale diapirism and deep with sedimentation. Post-depositional faulting is believed to have controlled the configuration of the Geopressure surface and has played later roles in modifying the present day depth to top of Geopressures. In general, Geopressure in this area is often associated with simple rollover structures bounded by growth faults, especially at the hanging walls, while hydrostatic pressures were observed in areas with k-faults and collapsed crested structures.
Selim Simon Shaker - One of the best experts on this subject based on the ideXlab platform.
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strat Geopressure fairways the fast track to prospect evaluation case history from the gulf of mexico
2016Co-Authors: Selim Simon Shaker, Walter W WornardtAbstract:Abstract The newly introduced strat-Geopressure mapping technique can highlight the optimum fairways to further exploring in semi-mature areas. It delineates the spatial favorable potential producing targets at a progressive stratigraphic sequence fashion. It also assesses the bypass and potential reservoirs that have been discarded due to old logging measurements, drilling challenges and resources restrictions. This method is greatly helpful where seismic attributes, especially amplitude variations with offset (AVO), misidentify the pay vs. wet sands. In addition to finding the low risk prospects where economic feasibility is very promising, pore pressure, mud, and casing programs can be easily predicted prior to drilling the prospect. The non-seismic method of assessing, delineating and mapping the optimal exploration fairway at each stratigraphic unit is introduced in this paper. The concept of incorporating regional maximum flooding surfaces (MFS), at different stratigraphic units, and the top of Geopressure (TOG) in a mappable fairways fashion is the foundation of this technique. The ‘strat-Geopressure fairway‘ represents the adjoining spatial belt where mapping contours of the stratigraphic top and top of Geopressure meet. Integrating the established producing horizons (from the offset wells) to these fairways provides an essential fast track tool for pre-drilling appraisal of a play concept, lead and prospect. Furthermore, the abundance of geological, geophysical, and engineering data, and infrastructure facilities on the shelf can make these semi-mature areas a high exploration prospective in Louisiana and Texas Offshore areas. A case history from Galveston and High Island offshore Texas is presented as a pilot study.
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Velocities Crossover Due to Geopressure: Implication to AVO Assessment
SEG Technical Program Expanded Abstracts 2009, 2009Co-Authors: Selim Simon ShakerAbstract:There is a fundamental quest to assess the impact of pore pressure profile on the AVO analysis. This abstract explores the effect of the subsurface Geopressure impact on the assessment of the conventional AVO three classes. In clastic sediments, the maximum and minimum principal stresses are the driving mechanism in determining the change of porosity and, consequently, the Geopressure profile. Therefore, the changes of pore pressure have a substantial impact on the petrophysical properties (Vp, Vs and ρ) and the seismic attributes. The velocities of sand (reservoir) and shale (seal) perform dissimilarly when they are subject to the overburden stress. The reservoir sand follows a power line trend with the increase of overburden. On the other hand, shale velocity and density incrementally increase with depth down to the top seal (top of Geopressure). Below the top of Geopressure, shale velocity substantially retreats.
Jeffrey A. Nunn - One of the best experts on this subject based on the ideXlab platform.
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geothermal and Geopressure assessment with implications for carbon dioxide sequestration lower tuscaloosa formation louisiana
2012Co-Authors: Timmon Drumm, Jeffrey A. NunnAbstract:Abstract Proximity to near-term anthropogenic carbon dioxide sources and existing infrastructure make Louisiana a desirable location for carbon capture and storage. Spontaneous potential, gamma ray, and resistivity logs from 96 wells were used in a regional scale evaluation of the Massive Sand Member of the lower Tuscaloosa Formation in Louisiana for carbon dioxide sequestration. Subsurface depths to the top of the Massive Sand Member range from roughly 750 m to 6400 m (2460–21,000 ft) with a regional basinward dip. Gross sandstone isopach reveals substantial sandstone thicknesses with a general trend of thickening basinward. Reservoir temperatures, estimated from corrected bottom hole temperatures, range from 44°C to 196°C (111–353°F) with an average regional geothermal gradient of 0.029°C/m (1.6°F/100 ft). Reservoir pressures, determined from mud weight data, indicate a pressure range from 8 MPa (1160 psi) in north Louisiana to 71 MPa (10,300 psi) in the deepest locations. Under these conditions, carbon dioxide should be in a supercritical phase with densities of 200–750 kg/m3 (13–50 lbs/ft3). Regionally, the Massive Sand Member varies from normally pressured in the north to Geopressured in the south. However, locally thick sandstones, greater than 45 m (150 ft) located in Pointe Coupee, East Feliciana, East Baton Rouge, and Livingston parishes in central Louisiana appear to be normally pressured even though they are below the regional top of Geopressure trend. Volumetric estimation suggests the area could sequester over 80 million metric tons (176 billion lbs) of carbon dioxide.
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EFFECTS OF COUPLED CONVECTION AND CO2 INJECTION IN STIMULATION OF GeopressureD GEOTHERMAL RESERVOIRS
2011Co-Authors: Tatyana Plaksina, Christopher White, Jeffrey A. Nunn, Taylor GrayAbstract:Geopressured brines are a vast geothermal resource in the US Gulf of Mexico region. In particular, Geopressured sandstones near salt domes are potential sources of geothermal energy because salt diapirs with high thermal conductivity may pierce younger, cooler strata. These characteristics enhance transfer heat from older, hotter strata at the base of the diapir into shallower strata. Moreover, widespread Geopressure in the Gulf region tends to preserve permeability, enhancing productivity. As an example, the Camerina A sand of South Louisiana was chosen as a geomodel for a numerical simulation study of effects of CO2 injection and wellbore cooling as the innovative method of geothermal development. This paper presents scenarios for heat harvesting from typical Gulf of Mexico Geopressured aquifers including Camerina A that take advantage of coupled convection and simultaneous CO2 sequestration. A suite of TOUGH2 numerical simulations demonstrates benefits of introducing CO2 injection wells, varying locations of injection/production segments of wells, and exploiting gravity segregation of the fluids.