Bahram Alizadeh

Artificial neural network modeling and cluster analysis for organic facies and burial history estimation using well log data: A case study of the South Pars Gas Field, Persian Gulf, Iran

Intelligent and statistical techniques were used to extract the hidden organic facies from well log responses in the Giant South Pars Gas Field, Persian Gulf, Iran. Kazhdomi Formation of Mid-Cretaceous and Kangan-Dalan Formations of Permo-Triassic Data were used for this purpose. Initially GR, SGR, CGR, THOR, POTA, NPHI and DT logs were applied to model the relationship between wireline logs and Total Organic Carbon (TOC) content using Artificial Neural Networks (ANN). The correlation coefficient (R^2) between the measured and ANN predicted TOC equals to 89%. The performance of the model is measured by the Mean Squared Error function, which does not exceed 0.0073. Using Cluster Analysis technique and creating a binary hierarchical cluster tree the constructed TOC column of each formation was clustered into 5 organic facies according to their geochemical similarity. Later a second model with the accuracy of 84% was created by ANN to determine the specified clusters (facies) directly from well logs for quick cluster recognition in other wells of the studied field. Each created facies was correlated to its appropriate burial history curve. Hence each and every facies of a formation could be scrutinized separately and directly from its well logs, demonstrating the time and depth of oil or gas generation. Therefore potential production zone of Kazhdomi probable source rock and Kangan- Dalan reservoir formation could be identified while well logging operations (especially in LWD cases) were in progress. This could reduce uncertainty and save plenty of time and cost for oil industries and aid in the successful implementation of exploration and exploitation plans.

Investigating Geochemical Characterization of Asmari and Bangestan Reservoir Oils and the Source of H2S in the Marun Oilfield

Abstract Geochemical evaluation is one of the most important and applicable methods for optimization of hydrocarbon exploration and production. In this article, the geochemistry of Asmari and Bangestan reservoir oils of Marun oil field was experimentally studied. Marun oil field is one of the giant oil fields in southwest Iran and has two oil reservoirs (Asmari and Bangestan) and one gas reservoir (Khami). The main goal of this study is to investigate the genetic behavior of the above oil reservoirs, focusing mainly on hydrogen sulfide pollutants. Biomarkers of saturated and aromatic fractions were studied on five polluted, three unpolluted Asmari, and two Bangestan reservoir oils. A triangular diagram was used to determine the chemical composition of the studied oil. The results show relatively higher oil maturity for both reservoirs with no biodegradation. The carbon preference index of both reservoir oils was also around 1, which indicates mature oil samples. The pristane-to-phytane ratio, Pri/nC17 versus Phy/nC18, terrigenous/aquatic ratio (TAR), and geochemical data all show that the source rock for both Asmari and Bangestan reservoirs is the same. This source rock was deposited in a reducing environment with algae (kerogen type II) organic matter and without any higher plants. Genetic potential studies of probable source rocks, by means of Rock-Eval VI analysis in Marun oilfield, present Kazhdomi and Garu as main source rocks. Biomarkers of sulfur compounds and structural analysis of Marun oil field revealed that hydrogen sulfide gas pollution in the Asmari reservoir originated from the Bangestan reservoir. In addition, thermal sulfate reduction was a possible main process for hydrogen sulfide formation.

Correlation of Oils and Source Rocks in Marun Oil Field in the South West of Iran: Using Biomarkers

Biomarkers study is one useful tool for oil-oil and oil-source correlations in any petroleum field. Molecular markers were used together with stable carbon isotopes to constrain genetic relationships between oils and potential source rocks in the Marun oil field. The Marun oil field is one of the giant oil fields in south west of Iran. It consists of two oil reservoirs named Asmari and Bangestan. This article presents the correlation of Asmari and Bangestan oil reservoirs with probable source rocks named Pabdeh, Kazhdomi, and Garau formations. Distribution patterns of different biomarkers, such as Hopanes and Steranes (obtained by gas chromatography-mass spectrometry), were used to correlate oils and source rocks. The results show that there is an obvious similarity in distribution patterns of all biomarkers between Kazhdomi formation and oil samples as compared with Pabdeh and Garau formations. Furthermore, stable carbon isotope shows that in contrast to Pabdeh and Garau formations, the carbon isotope range of Kazhdomi formation had a good overlaying with Asmari and Bangestan oil reservoirs. The result of this study shows Kazhdomi formation as a proper source rock of oil in the Marun oil field.

An Investigation of Hydrogen Sulfide Plume Migration in the Asmari Reservoir of the Iranian Marun Oil Field: Using Repeat Formation Tests

Marun oil field is one of the giant oil fields in southwest of Iran. It consists of two oil reservoirs and one gas reservoir named Asmari, Bangestan, and Khami, respectively. One of the major problems in this field is contamination of Asmari reservoir with H2S gas. The aim of this article was to study the trend and history of H2S spreading in Asmari reservoir of Marun oil field and also to investigate communication of Asmari reservoir layers via evaluation of fracture distribution, horizontal and vertical permeability distribution, and repeat formation test results. The results demonstrated good communication of layers in the center, especially in sectors 4 and 6 of the southern limb, central part of Asmari reservoir, due to higher fracture, higher permeability, and good pressure communication in these sectors. Moreover, the history of H2S concentration during time showed a decreasing trend while this contamination is spreading from the southeast to northwest of Asmari reservoir.