Student, Federal University of Technology Akure,Nigeria
Stratigraphic Analysis and Static Modeling of Olu Field using 3-D seismic and Biofacies data
Detailed integrated studies using biostratigraphy and other datasets available from two wells were carried out. The result obtained from the analysis of this data was then used to validate the information on the well logs and extrapolate for other wells with no biostratigraphy dataset. A chronostratigraphy correlation was then carried out across the eight (8) wells and two hydrocarbon bearing sand units (Reservoir O and Q) were delineated and mapped on the seismic section via the synthetic seismogram. Structural time maps for were generated for both reservoirs. A second order polynomial function was then generated from the plot of depth (Z) against two-way travel time (TWT) of the checkshot data. The resulting function was then used to build a velocity model which was used to convert the structural time maps to structural depth maps. The structural depth maps were then overlaid on the structural depth maps to validate if both maps are trending in the same direction. Detailed petrophysical analyses of the field were also carried out. In order to capture the heterogeneity and randomness within the reservoir so as to arrive at a final well and production behavior made it necessary to construct a fit for purpose geological models for the reservoir using stochastic methods such Sequential Gaussian Simulation algorithm, Sequential Indicator Simulation, Kriging, etc. Cross plots of several elastic properties such as murho, lamdarho, vp, vs ,etc were also carried out. This was done in order to observe the degree of cementization within the reservoir and its effect on the connectivity of the reservo Five maximum flooding surfaces (MFs) were identified from the biostratigraphy analysis. The identified MFs include; Dodo shale (11.4Ma), Nonion-4 (10.4Ma), Uvigerna-8 (9.5Ma), an unnamed shale marker (7.4Ma) and Haplophragmoides -24 (5.0Ma). The stratigraphic analysis of the field also revealed that the reservoirs within the field have high potential for hydrocarbon accumulation since they occur mostly in the channel and upper shoreface depositional environment of the highstand systems tract. The shale found within the transgressive systems tract of the field helped to form a good stratigraphic trapping mechanism within the field. The modeled reservoir has an average porosity of 0.25, average permeability of 1036mD, an average water saturation value ranging from 0.16 - 0.52. The cross plots revealed that the reservoirs have little amount of cement
Abstract: An important hydrocarbon reservoir is hosted by the third member of the Shahejie Formation (Es3) in the Zhanhua Sag, Bohai Bay Basin. Seismic stratal slices reveal different characteristics of channels and fan-delta lobes between the south (slope break belt) and southwest (gentle slope) areas combined with lithology, wire-line logs and three-dimensional (3-D) seismic data in the southern slope of Zhanhua Sag. And an excellent analogue has been provided for understanding various key depositional evolution of fan-deltas in the slope system (from base to top: Es3L, Es3M and Es3U). The Sedsim, a three-dimensional stratigraphic forward modelling programme, is applied to simulate the evolution of fan-deltas in the southern slope break systems and southwestern gentle slope systems of the Zhanhua Sag by considering a number of key processes and parameters affecting the fan-deltaic deposition from 43 Ma to 38.2 Ma. Modelling results indicate that depositional types and scales evolved from the thickest medium-scale gravel- or sand-rich fan deltas (43 Ma ∼41.4 Ma, Es3L) to the thinnest small-scale mud-rich fan deltas and lacustrine mud (41.4 Ma ∼39.8 Ma, Es3M), and lastly to less thicker larger-scale mixed sand-mud fan deltas (39.8 Ma ∼38.2 Ma, Es3U). The types of slope system, sediment supply and lake-level change are three controlling factors for determining the source-to-sink architecture of the gravel-to mud-rich fan-deltas and sediment-dispersal characteristics. This study has demonstrated that the process-based modelling approach can be effectively used to simulate complex geological environments and quantify controlling factors.
Pub.: 03 Nov '16, Pinned: 23 May '18
Abstract: Publication date: August 2018 Source:Journal of Petroleum Science and Engineering, Volume 167 Author(s): Hamed A. Alrefaee, Sayantan Gosh, Mohamed I. Abdel-Fattah We used high-resolution 3D seismic data and applied seismic attribute analysis to geometrically interpret and characterize the polygonal fault systems in the Paleocene-Eocene sequence of the Rankin Platform Sub-basin, Northern Carnarvon Basin, Australia. The polygonal faults were identified in a stratigraphic sequence dominated by calcareous clay with minor calcilutite at its lower section that changes to argillaceous calcilutite and calcareous claystone at its upper section. Seismic sections and time slices, through multi-attribute (coherence, energy ratio similarity, and curvature) volumes display a dense distribution of normal faults with polygonal shape and small throws in the plain view. The polygonal fault systems (PFS) exist in two well-defined tiers, which can act as pathways for the fluid flow migration. The first tier coincides with the upper section (Early-Middle Eocene Wilcox Formation) with a few faults and the second one coincides with the lower section of the sequence (Paleocene Lambert and Dockrell formations) with a greater number of faults. Proper understanding and interpretation of the polygonal fault systems as non-tectonic extensional faults are a critical issue in assessing the migration pathway for hydrocarbon (gas) through the Paleocene-Eocene sequence in the Northern Carnarvon Basin, and elsewhere in the world.
Pub.: 25 Apr '18, Pinned: 23 May '18
Abstract: Publication date: May 2018 Source:Marine and Petroleum Geology, Volume 93 Author(s): Bassem S. Nabawy, Mohamed S. El Sharawy The middle Miocene Kareem Formation represents one of the most important reservoirs in the Gulf of Suez, Egypt. Six boreholes locating throughout different structural trends in the Southern province of the Gulf of Suez, Egypt, were selected to study the reservoir properties of the Kareem Formation. The study depends on integrated data of well logs and routine core analysis as well as seismic data. The present study is an integrated study aims to study and discriminate the reservoir quality of the Kareem sequence using various statistical techniques. Testerman statistical approach and stratigraphic modified Lorenz (SML) plot were used in reservoir zonation. Principal Component Analysis (PCA) and cluster analysis were used to identify the electrofacies distribution within the studied formation. The well log data enabled characterizing the reservoir sequence into 6 electrofacies. The available core analyses data and core description for the Kareem Formation (850 feet cored interval) in Morgan oil field enabled more accurate discrimination for the reservoir sequence into 13 hydraulic flow units (7 of them are potential flow units). The studied sequence is differentiated into five lithologic-petrophysical facies; siltstone, dolomitic siltstone, dolomitic sandstone, sandstone and friable sandstone. The sandstone and friable sandstone facies are the best petrophysical facies. The dolomite content is the main key factor for reducing the reservoir quality of the studied Kareem sequence. From the core data, a total net pay thickness of 180 feet (mostly composed of sandstone with some siltstone intercalations) was assigned of fair quality (∅He = 14.7%, kH = 89.1 md, So = 28.8%, reservoir quality index ‘RQI’ = 0.60 μm, flow zone indicator ‘FZI’ = 3.81 μm, reservoir potential index ‘RPI’ = 2) with few streaks of good to very good potential. However, the siltstone samples have less petrophysical potential than the sandstones.
Pub.: 15 Apr '18, Pinned: 23 May '18
Abstract: Studying the geologic architecture of the Xiong’an New Area will provide important basis for the evaluation of crustal stability, urban planning and infrastructural projects in this region, and it is also of great significance in exploring the occurrence of oil and gas, geothermal, hot dry rock and other resources. The stratigraphic system of the study area is established by using latest high quality seismic reflection and deep borehole data. Characteristics of the major faults developed in the study area are finely depicted with the method of structural analysis. Tectonic evolution of Xiong’an and adjacent areas is reconstructed by using balanced geological cross-section technique. The tectonic activity of the study area is discussed on the basis of the development of secondary faults and the distribution of active earthquakes across the region. This study demonstrates that Xiong’an New Area is located at the transfer zone of the central and northern Jizhong Depression. There are three regional unconformities developed in this area, by which four structural layers are sub-divided. Controlled by the Taihang Mountain piedmont fault, the Daxing fault, the Rongcheng fault and the Niudong fault, the structural framework of the study area is characterized by intervening highs with sags. This structural pattern has an important controlling over the reservoir characteristics, hydrocarbon accumulation and the distribution of geothermal resources and hot dry rock within this region. Rifting in this area began in the early Paleogene, exhibiting typical episodic character and became inactive in Neogene. The development feature of secondary faults along with the distribution of active earthquakes indicate that Xiong’an New Area has been in a relatively stable tectonic setting since the Neogene, while the Baxian Sag and other structural units to the east of it have obviously been in a rather active environment.
Pub.: 02 May '18, Pinned: 23 May '18