Development, Evolution, and Episodic Charge History of Pop-up Structures in Southeast Abu Dhabi, UAE

The main goal of this paper is contributing to the understanding to the structural geology, development, and evolution of traps associated with strike-slip restraining bend and restraining step-over structures as a key petroleum system element in southeastern Abu Dhabi. We introduce a preliminary classification scheme for these relatively small, low-relief features defined here as pop-up structures. These structures represent different evolutionary stages of strike-slip restraining bends formed along prominent WNW-trending strike-slip fault systems in southeastern Abu Dhabi. The proposed classification scheme was summarized as a chart to illustrate the correlation between the degree of structural deformation and seal integrity, and estimates the likelihood of finding multiple, vertically stacked, productive reservoirs. It also leads to a more detailed discussion on others important characteristics of pop-up structures and provides a better understanding of sealing mechanisms such as fault juxtaposition, fault throw analysis, fault slip tendency, fault rock processes, and the role of the development of hybrid flower structures in the area. We will also show a simple case study based on two exploratory wells that targeted two pop-up structures with different degrees of deformation in southeast Abu Dhabi. This case study illustrates the complex relationship between pop-up evolution, timing of trap formation, seal integrity, trap preservation, and multiple petroleum generation and migration events. Pop-up structures are linked to multiple episodes of trap and seal evolution, where several episodes of hydrocarbon migration, charge, and leaking of hydrocarbons may occur.

Five Decades Of Petroleum Exploration And Discovery In The Malay Basin (1968-2018) And Remaining Potential

Since the first oil discovery in the Malay Basin in 1969, more than 700 exploratory wells have been drilled. To date, there are more than 181 oil and gas discoveries, about half of which are currently in production and about a dozen are already in their secondary or tertiary recovery stages. In 2014 it was estimated that a total of over 14.8 billion barrels of oil equivalent (bboe) of recoverable hydrocarbon resource have been discovered in the basin, contributing to approximately 40% of the total hydrocarbon resources of Malaysia. By the end of the first decade of exploration in 1979, all the major basin-centre anticlinal structures had been tested. This play type contributed 60% of the total discovered resource in the basin. By 1981 this most prolific play type had been practically exhausted, as all the giant fields (those with recoverable resource > 0.5 bboe) had been found. As “creaming” of the basin-centre anticlinal play continued into the early 1980s, exploration efforts gradually shifted to the newly discovered western margin play types, particularly in the Western Hinge Fault Zone, Tenggol Arch and the adjacent Penyu Basin. There was a “lull” period from 1985 to about 1990, due to the global oil crisis, after which exploration was rejuvenated through significant discoveries in several play types on the northeastern ramp margin. This followed a successful drilling campaign that lasted until around 1997 and contributed an additional ~1 bboe of recoverable resources over a seven-year period. Since then, most of the incremental resource addition came from the highly gas-charged play in northern region that comes under the Malaysia-Thai Joint Development Area (JDA) and on the northeastern ramp margin, which includes the Commercial Arrangement Area (CAA) between Malaysia and Vietnam. Individually, however, the hydrocarbon volumes in these later discoveries were relatively small compared to the earlier discovered play types. Subsequently, new play types were pursued, including stratigraphic channels, deeper reservoirs beneath existing fields, high pressure/high temperature (HPHT) reservoirs, overpressured and tight reservoirs, and fractured basement reservoirs. All had some measure of success but none were able to volumetrically match the discoveries made decades earlier. As of end of 2018, over 2100 exploration and development wells had been drilled in the entire basin. Based on the creaming curve, since around 1990 and into the fifth decade of exploration, the incremental resource addition has been increasing steadily at an average rate of ca. 120 MMboe per year. The data indicate that the expected average discovery size would be less than 25 MMboe, and that at least 5 wells need to be drilled per year to sustain the same rate of resource addition. If no new plays are explored and no significant discoveries made, resource addition is expected to plateau beyond 2020. The basin needs a new stimulus, and more importantly, new exploration play concepts to sustain exploration business.

THE GEOLOGICAL ROLE OF THE SEARCH METHOD "WILD CAT WELLS" IN THE STUDY OF THE HYDROCARBON POTENTIAL OF THE PRIPYAT TROUGH

The results of geological exploration for oil within the Elsky, Shatilkovsky, Savichsky and Petrikovsko-Shestovichsky sections of the Pripyat trough are analyzed. The analysis covers almost 70 years from the drilling of the first exploratory wells laid by the "wild cat" method to the modern comprehensive justification. During the analyzed period, from 12 to 23 deep wells were drilled with a total penetration of 42.3 thousand meters to 68.3 thousand meters in each section. The initial stage of work after the first oil inflow is characterized by a higher activity of drilling new exploratory wells, justified by the methods available at that time. The negative result of exploratory drilling in certain areas is also due to the significant fragmentation of the intrasalt perspective horizons and the areal unevenness of reservoir layers in the subsalt complex. Within the boundaries of the sites, deposits with recoverable oil reserves of no more than 450 thousand tons are established, which can be determined as a low economic efficiency of prospecting operations. However, the work has played a positive role in determining real models of hydrocarbon traps for use in the study of other sites.

Mass balance of Neogene sediments in the Colombia basin relationship with the evolution of the Magdalena and Cauca River basins

The Colombia basin contains large volumes of sediment accumulated during the last 17 My. The use of isochore maps, exploratory wells, micropaleontological and geochronological dates has enabled us to estimate the volumes of sediment and accumulation rates in this basin. The analysis of source of sediments and exhumation data from the Northern Andes of South America led to the definition of areas and thicknesses of material eroded during the Neogene - Quaternary, to obtain volumes or material eroded from the continent that can be correlated with sediment volumes accumulated in the Colombia Basin. The analyzed sediment volumes suggest that during the last 17 My ~72.06x1015 Tons accumulated in the Colombia Basin, while ~ 7.16x1013 Tons accumulated in the continental catchment areas. The sedimentation in the Colombian Basin has occurred at variable rates, with values ranging from 55 MTons/My to 295 MTons/My, with a peak of 803 MTons/My in the early Pleistocene (between 2.4 and 2.2 Ma). The evaluation between the total volumes of sediment accumulated in the offshore and onshore, suggests that in the continental part of the basin less than 4% of the total volume of eroded sediment is trapped and, therefore, the behavior of the accumulation rates calculated in the offshore directly reflect the relief evolution of South America’s Northern Andes. It seems, at large, that the lithospheric convergence rates and subduction angle (South America vs Nazca and Meso Atlantic opening) have controlled the regional exhumation of the Northern Andes, with the exception of the Pleistocene high sedimentation event, which seems to coincide with local events such as the collision of the Panama Arch against Western Antioquia. It may be concluded that thanks to this collision, drainage systems such as those of the Magdalena and Cauca rivers were modified, which resulted in the formation of the Magdalena Submarine Fan.

A novel method for fracture pressure prediction in shallow formation during deep-water drilling

A large numbers of deep-water drilling practices have shown that more than 60% of deep-water wells have the complex leak-off during the drilling process, which poses great difficulties and challenges for the safety and operation time of deep-water drilling. The purpose of this article is to establish a method for predicting the fracture pressure in shallow formations. In this study, the deep-water shallow formation was divided into the upper unconsolidated soil layer and the lower diagenetic rock layer according to the geotechnical distribution characteristics of the deep-water shallow formation. The location of the transition soil/rock layer zone was determined using the upper soil layer density trend line and the lower rock layer density log data regression trend line. The deep-water shallow fracture pressure prediction model was established based the soil/rock transition zone. Shear failure criterion was used above the transition zone and tensile failure criterion is used below the transition zone. The shallow fracture pressure of 6 drilled exploratory wells in the X block from the South China Sea were calculated using this new method and the calculation errors were all less than 3.18%. Moreover, the shallow fracture pressure body in this block was established using the Kriging interpolation method based on 6 drilled exploratory wells data. This shallow fracture pressure body established here were used to predict 9 development wells shallow fracture pressure with a predictive error less than 1.7% and there were no drilling accidents. The case study demonstrates that the new model can significantly improve the prediction accuracy, has good prospects for popularization and application.

Structural and Economic Analysis of Meyal Oil Field in the Northern Potwar Deformed Zone, Upper Indus Basin, Pakistan

Potwar sub-basin is famous for its structural style, hydrocarbon exploration and production activities from Cambrian to Pliocene rocks. Foreland basin related subsurface structures, in the presence of source and seal rocks offer a variety of traps to host hydrocarbons. Meyal Oil field, situated in the NW Potwar sub-basin, is a hydrocarbon resource for the country. Subsurface structures of Meyal area were outlined by interpreting two strike and four dip lines in IHS Kingdom suite. Borehole data of MYL-10, MYL-12 and MYL-13 exploratory wells were incorporated to improve the subsurface understanding. A total five prominent reflectors of Permian, Triassic, Jurassic, Paleocene and Eocene rocks were marked on the seismic sections. The seismic interpretation shows a post Eocene pop-up structure flanked by a back thrust and a fore thrust. Moreover, the time structure maps for Meyal area display a doubly plunging and faulted anticline as a result of south directed compression. Four isochron maps show thickness variation in Permian to Eocene sediments in the study area. The results of interpretation show favorable structural trap for economic hydrocarbon exploration.

Analysis of subsurface structural trend and stratigraphic architecture using 2D seismic data: a case study from Bannu Basin, Pakistan

The present study is focused on the subsurface geology of Bannu Basin, a part of western Indus foreland Pakistan. For this purpose, some regional seismic profiles and deep exploratory wells data have been used in integration.A total of ten mappabale seismic reflection events have been identifed which are representative of specific geological units. In general, based on the seismic the formation trends, the horizons are dipping in the northwest direction of the study area. The area generally deepens toward the northwest due to sediments load toward the northwest. The seismic profile MWI-83 shows a unique faults bounded anticlinal structure that has also been mapped on the two-dimmensional contour maps. This could be regarded as potential hydrocarbon entrapment. The regional seismic profiles are contoured for the entire grid in both time and depth domain to obtain the clearer image of the subsurface individual stratigraphic units. The 2D contour maps for Lower Permian aged Warcha Sandstone, Middle Triassic aged Tredian Formation and Early Jurrasic aged Datta Formation have been prepared using gridded TWT of the seismic profiles. The time and depth contour maps of the Datta Formation and Tredian Formation show a four way clouser oriented in the southeast dierction. The area of the closure was computed which is 24 Sq km approximately. Furthermore, the formation tops of the five wells have been used to correlate the wells for understanding the lateral and vertical variations in the stratigraphic layers. The correlation shows that the Datta Formation’s thickness increases at the centre of the basin whereas decreases on the east and south flanks of the basin. Reasons of Wells failure were concluded on the basis of the final well report and concluded that these well failure occur due to poor quality of the data and also due to some mechanical problems. Reservoircharacterization using statistical rock physics and petrophysics coupled with core data analysis can provide further insights into the hydrocarbon exploration.

Results of geological and geophysical research on the Subotska structure of Ingulskiy megablock of the Ukrainian shield

The article presents the results of diamond prospecting studies in the Subotska structure of the Inhulskyi megablock of Ukrainian Shield. For the results, it is indicated that the Subotska structure is mimicked by crater rocks and in some cases by manifestations of the vent facies with signs of kimberlitic-lamproitic magmatism. The typical local features of manifestations of explosive structures from maar volcanism in Subotska area are determined. The article presents the results of petrographic and mineralogical study of the core material from exploratory wells on the Subotska structure, the results of study of material composition of the clay fraction, X-ray diffraction analysis of the pellet fraction. Data of the X-ray structural analysis of the pellet fraction of samples taken from the core material from exploratory wells on the Subotska structure indicates the obvious mechanical sum, the head folder of such is calciferous montmorilonite, and also saponite, nontronite, hydromica and kaolinit. The availability of the nontronite and saponite is confirmed by the results of electronic-microscopic reports. Also the article presents the results of studying the secondary lithochemical halos of Cr, Ni, Mg, Co, Ti, V, Fe, covering the geochemical spectrum inherent in alkaline-ultrabasic rocks and their weathering crust. These halos are combined with negative gravitational anomalies associated with the explosive structures in the Subotska area. The structural control of the great part of the detected geochemical anomalies, geochemical halos are determined. According to the degree of manifestation of the complex of criteria five potential diamond-prospective structures are discovered on the Subotska area. There were developed recommendations for further research on the Subotska area.

Crude Oil Classification Based On Age And Provenance From The Southern Iraq: A Review

A collection of 165 crude oils, 12 oil seeps, and 24 extracts and recovered samples from 25 oil exploratory wells and 6 oil seeps in the Southern Mesopotamian Basin were studied. Biomarker configurations and other organic geochemistry parameters were used to discover the depositional environments and to classify the oil samples as provenance groups. Petroleum liquids were geochemically classified into four groups. The first group of oils, Middle Jurassic Zagros Fold Belt, is located in the Maysan, Basra, and Thi qar provinces of the basin that has pristane/phytane (Pr/Ph) proportions ≤0.97 and contains sufficient gammacerane. Methylphenanthrene index 1 (MPI 1) values show that the first group of oils is mature. Oils from Group 2, Upper Jurassic–Lower Cretaceous Sulaiy/Yamama, by disparity have Pr/Ph proportions between 0.72 and 1.12 and relatively moderate C28/C29 steranes, 0.52-0.88. Ts/Tm ratios indicate thermal maturity for Group 2 oils. Unlike oils from other groups, the oils from Group 3, Cretaceous to Tertiary oils, in Subba Field hold the highest canonical variable (CV) values that range between 0.43 and –2.30. The fourth group, Late Triassic-Middle Jurassic oil seeps, is the oldest among all groups. This group holds an average carbon isotope ratio –28.25‰ and –28.10‰ for saturates and aromatics respectively, which are the lowest values among all oils in the studied region. The Tithonian-Berriasian Sulaiy/Yamama oils further divided into three subgroups. The first subgroup, A, has carbon preference index (CPI) values of ≤1.08 (average 0.86) and C28/C29 sterane of 0.56-1.13 with an average of 0.65. Second subgroup, B, holds CPI ≤1.18 (average 0.99) and C28/C29 sterane 0.55-0.82 with an average of 0.63. The last subgroup, C, has CPI values ≤0.93 (average 0.85) and high C27 and C29 steranes (average 46.5% and 39.61%, respectively). In the same way, the Group 3 can be further subdivided into two subgroups based on values of carbon isotopes for saturates and aromatics. The oils from this group are heterogeneous and can be further divided into Tertiary Subgroup and Cretaceous Subgroup.

DELINEATION OF HYDROCARBON SATURATED RESERVOIR SAND USING INTEGRATED 3D PRE-STACK SEISMIC AND WELL LOG DATA IN BONGA – FIELD, CENTRAL SWAMP DEPOBELT, ONSHORE NIGER DELTA, NIGERIA

This study has successfully delineated the lateral continuity of hydrocarbon saturated sand reservoir in Bonga field, Niger Delta. 3D pre-stack seismic volume and well logs from two (2) exploratory wells were employed in the pre-stack seismic inversion analysis. The delineated BGA reservoir sand spans across the two (2) wells labelled Bonga-26 and Bonga-30. The reservoir depth ranges from 10490 ft to 10620 ft in Bonga-26 while the reservoir depth ranges from 10390 ft to 10490 ft in Bonga-30. The delineated reservoir is characterized by low gamma ray (< 75 API), water saturation, shale volume and high resistivity as deciphered in their respective well log curves signature. Rock attribute crossplot was carried out to discriminate between the formation fluid and lithology. The crossplot space of VP-VS ratio versus acoustic impedance (AI), discriminates the formation properties into lithology and fluid (gas and brine sand) based on clusters inferring the presence of each formation fluid properties. The inversion cross sections of P-impedance, S-impedance, density (ρ) and VP-VS ratio depicts the spread and lateral continuity of the reservoir sand across the well locations. The delineated zones reveal low P-impedance, density, VP-VS ratio and slight increase in S-impedance which further validate the presence of hydrocarbon in the field.