Reservoir characterization and modeling of lateral heterogeneity using multivariate analysis

Reservoir characterization deals with the description of the reservoir in detail for rock and fluid properties within a zone of interest. The scope of this study is to model lateral continuity of lithofacies and characterize reservoir rock properties using geostatistical approach on multiple data sets obtained from a structural depression in the bight of Bohai basin, China. Analytical methods used include basic log analysis with normalization. Alternating deflections observed on spontaneous potential (SP) log and resistivity log served as the basis for delineating reservoir sand units and later tied to seismic data. Computation of variogram was done on the generated petrophysical logs prior to adopting suitable simulation algorithms for the data types. Sequential indicator simulation (SIS) was used for facies modeling while sequential gaussian simulation (SGS) was adopted for the continuous logs. The geomodel built with faults and stratigraphical attitude gave unique result for the depositional environment studied. Heterogeneity was observed within the zone both in the faulted and unfaulted area. Reservoir rock properties observed follows the interfingering pattern of rock units and is either truncated by structural discontinuities or naturally pinches out. Petrophysical property models successfully accounted for lithofacies distribution. Porosity volume computed against SP volume resulted in Net to gross volume while Impedance volume results gave credibility to the earlier defined locations of lithofacies (sand and shale) characterized by porosity and permeability. Use of multiple variables in modeling lithofacies and characterizing reservoir units for rock properties has been revisited with success using hydrocarbon exploration data. An integrated approach to subsurface lithological units and hydrocarbon potential assessment has been given priority using stochastic means of laterally populating rock column with properties. This method finds application in production assessment and predicting rock properties with scale disparity during hydrocarbon exploration

APPLICATION OF ROCK AND SEISMIC PROPERTIES FOR PREDICTION OF HYDROCARBON POTENTIAL

This study explores the use of well logs and seismic derived rock properties to predict hydrocarbon potentials. Crossplot analysis of well log data and seismic attributes extracted and captured over some depth windows from the vicinity of the prolific hydrocarbon zone was the main methodology. This made it possible to develop relationships through cross-plotting of different log types and different seismic attributes. Emphasis was placed on petrophysics based properties from well logs while the stratigraphic, complex and signal based seismic attributes were computed and analysed. Combination of one or more attributes was attempted in deriving a correlative relationship typifying the reservoir property. The well log derived properties predicted the hydrocarbon potential of the reservoir better as it gave better correlation of above 70% on the crossplots made. While seismic properties crossplots had poor correlation except those of signal based and complex attributes that gave negative correlations

Characterization of Rock Fabric and Fluid Fairway for Hydrocarbon Imprint and Lateral Prediction.

This work made use of computed data from well logs, with migrated seismic data, to evaluate rock fabric, reservoir fluid, and lithology of an unconsolidated alluvial fan deposit. Acoustic and elastic parameters amongst other logs were computed and used to characterize the subsurface reservoir. This was done to ascertain the possibility and success of well logs derived rock physics parameters in characterizing reservoirs. With the use of soft computing methods and stochastic algorithms, the objectives of this study were achieved. Results were presented in maps and model volumes. Lambda, Mu, Rho, and SP logs were the main inputs in the characterization based on both their individual potential and an integrated convolved potential. Filtered zones identified on cross-plot were applied to simulated volumes of LambdaRho and MuRho, gave good account of its ability to discriminate rock and fluid distribution. RGB visualization tool applied to the models gave a volume that was used to condition litho-units simulation with commendable results

Stratigraphy and reservoir quality of the turbidite deposits, western sag, Bohai bay, China P.R.

Stratigraphic and subtle reservoirs such as pinchouts, sand lenses and unconformities have been discovered in Bohai basin. These reservoirs occur in sub-basins and sag structures called depressions. A prolific depression is the Liaohe depression that has been filled with rapidly changing mixed alluvial fan deposit of the Cenozoic age. Attempts made at recovering residual hydrocarbon from the subtle reservoir have necessitated the re-evaluation of available data to characterize and model the prolific Shahejie Formation turbidite deposit occurring as pinchouts and sand lenses for hydrocarbon assessment, reservoir quality and possible recovery through enhanced methods. Methods employed covered well logs analysis, clustering analysis for electrofacies and fuzzy logic analysis to predict missing log sections. Stratigraphic and structural analysis was done on SEGY 3D seismic volume after seismic to well tie. Stochastic simulation was done on both discrete and continuous upscaled data. This made it possible to correctly locate and laterally track identified reservoir formation on seismic data. Petrophysical parameters such as porosity and permeability were modeled with result of clustering analysis. Result shows that electrofacies converged on 2 rock classes. The area is characterized by the presence of interbeded sand-shale blanket formations serving as reservoir and seal bodies. The reservoir quality of the formations as seen on the petrophysical analysis done is replicated in simulation volume results. Reservoir rocks have porosity between 0.1 and 0.25, permeability between 1 and 2mD and hydrocarbon saturation as high as 89%. Lithofacies are observed to be laterally inconsistent, sub-parallel to dipping and occurring as porous and permeable continuous beds or pinchouts hosting hydrocarbon. The stochastic stratigraphic model depicts rock units in associations that are synsedimentary. The prevalent configuration gotten from the model gave an insight into exploring and developing the field for enhanced oil recovery of the heavy hydrocarbon of this area

Integrated Multivariate Lateral Predictions For Reservoir Properties Via Geostatistical Modeling

Hydrocarbon production is a function of various elements such as reservoir quality, petrophysical properties, geophysical properties and also volume. Lateral extent of reservoir body is important information for estimation of hydrocarbon initially in place and the recoverable quantity. A method of integrated lateral prediction towards understanding reservoir geometry and rock properties towards enhanced hydrocarbon production is explored with dataset from Bohai bay, Northern China. The methods of conventional well log analysis, seismic interpretation and geostatistical modeling has been employed for this study. Computation of useful logs like Volume of shale, porosity, permeability, Acoustic impedance and Elastic impedance was primarily done on well logs followed by the identification of potential reservoir formation. Lateral extent of reservoir horizons was traced on seismic reflection data with precision through continuity and dominance. Seismic attributes were also computed to assist in better understanding of the characteristics of the rock units in structure and stratigraphy. Computation of variograms and data transformation was done prior to geostatistical simulations for all rock properties considered. The result shows an all encompassing realization on a static model of lateral rock properties within the zone of interest thereby making it easy for making decisions locating parts of the field with high values in rock and fluid properties as potential portions towards hydrocarbon production

A New Model for Predicting Elemental Sulphur Deposition in a Sour Gas Reservoir

This research work is concerned with developing a more accurate correlation for the prediction of elemental sulphur deposition in a sour gas reservoir by exploring the relationship between compaction and elemental sulphur deposition over time and also incorporating porosity damage caused by reservoir compaction into the previous models in order to obtain a more robust representation of what actually occurs in the reservoir. The models considered indicates that the established new model gives the most accurate, reliable and practical result in predicting sulphur deposition which suggests that the rate of sulphur precipitation is seemed to have been underestimated by previous models. This may have not been unconnected with the fact that the new model based on non-Darcy flow, incorporated the porosity reduction caused by reservoir compaction which has been hitherto neglected by previous works. Therefore, reservoir compaction is a common phenomenon, which should be considered in sulphur deposition prediction since it leads to a faster rate of sulphur deposition

Polymorphism of the testis-specific serine/threonine kinase 2 gene and risk of asthenozoospermia in Côte d'Ivoire

Background: The testis-specific serine/threonine protein kinase (TSSK2) is an indispensable protein responsible for the mobility of spermatozoa expressed specifically in the germ cells during spermatogenesis and present in the mature spermatozoa. Its gene mutation could constitute a risk of infertility. The aim of this study is to investigate the polymorphism of this TSSK2 gene in men with asthenozoospermia.Methods: The ejaculates were obtained from patients attending the reproductive biology unit of Institut Pasteur of Côte d’Ivoire for their spermiological evaluations. The semen analyses are performed with the automatic sperm analyzer SQA-Vision. 30 sperms, including 20 asthenozoosperms and 10 normosperms, were selected from their spermiological results and the spermatozoa DNA was extracted by the phenol/chloroform method. Direct Sequencing of the spermatozoa DNA fragments was done using the Sanger method. The frequencies of mutation were analysis with the Fisher and Mann-Whitney tests.   Results: It was revealed 17 mutations in 22 ejaculates. The frequent mutations are c.839C>T (T280M), c.816G>C (L372L), c.1026G>A (R342R), c.785A>C (H262P) and c.80A>G (K27R) with respectively frequencies of 50.0%, 26.67%, 16.67%, 13.33% and 10.0%. The analysis of these mutations indicated a significant difference in the frequency of occurrence of mutations between normosperms and asthenozoosperms (p-value = 0.01).Conclusions: This study shows that mutations in the TSSK2 gene are more common in asthenozoosperm ejaculates than normosperm ejaculates. This fact suggests the probable association of mutations in the TSSK2 gene with asthenozoospermia

Direct digital control of an efficient silicon+lequid crystal phase shifter

We demonstrate a phase shifter based on a silicon slot waveguide infiltrated with liquid crystal. We achieve a phase shift of 73 pi for a 5V drive voltage, with a voltage-length product of 0.022V.mm around 1V. We can drive the phase shifter directly with a 1V, duobinary pulse-width-modulated signal, allowing direct digital CMOS control of an analog optical phase shifter

The Contribution of a community-based organisation in challenging xenophobia through participation: a perspective from Site C, Khayelitsha

This article investigated the contribution of a community-based organisation; Site C, Action Committee Against Xenophobia in Khayelitsha, Site C, in challenging prejudice against African migrants. The purpose of the study was to explore the contributions of a Community-Based Organisation in Khayelitsha in fighting prejudice against foreign nationals in the country. This is vital as there is paucity or absence of information on the contribution of host communities in challenging prejudice and protecting migrants. The paper explains how SACAX mobilised the community and raised awareness towards the 2010 World Cup. To understand this phenomenon, the study employed mixed-method research comprising both quantitative and qualitative research. The qualitative research utilised in-depth interviews with six purposefully selected SACAX leaders and 10 members. Interviews were conducted with ward councilors and community development workers. Focus group discussions were conducted with 10 community members. The quantitative research comprised surveying 100 participants. Qualitative data were analysed using narrative and thematic techniques, complemented by the descriptive method. Also, factor analysis was used to analyse quantitative data. The study found that though xenophobia is endemic in the country, there are efforts by some individuals to combat it. This reveals that not all South Africans are xenophobic. The study concludes that through civic education xenophobia was nipped in its bud. It recommends the creation of an integrated framework involving all stakeholders involved in refugee management and extending this campaign nationwide to curb xenophobia. It also recommends future researchers investigate the challenges of local integration in South African cities

A New Model for Predicting Liquid Loading in Multiphase Gas Wells

Liquid loading problem occurs when there is accumulation of liquid in the wellbore. The ultimate desire of this phenomenon is to reduce gas recovery or completely kill the production well. This challenge can lead to loss in well deliverability and as a result recovery of gas becomes low and cause heavy damage that the remedy would be costly. So many scholars have modeled to predict liquid loading onset but over the years the results gotten have shown one discrepancies or the other and could be difficult to use because of the challenges facing in predicting the bottomhole pressure of a multiphase flow. Numerical integration method was used in this new model while considering the introduction of valve equation along the functional nodes to the fundamental equation. The pressure drop across the functional node has not been considered by previous scholars. The result is very effective when compared analytically with other established work. The results also show the onset of transient flow and how quickly it stabilizes. Furthermore, the numbers of correctly predicted wells when validated with data was higher than the previous result