Study of dependence between clay mineral distribution and shale volume in reservoir rocks using geostatistical and petrophysical methods

Identify and obtain a detailed understanding of shale and its clay minerals in three segments; exploration, drilling and reservoir in the oil industry are very important. The study of the formation clay minerals in terms of depth and layers of earth is done through X-ray tests on samples taken from the reservoir which in comparison with logging requires a lot more time and cost and also can't provide continuous results because continuous sampling from the whole well is not possible. NGS (Gamma-ray Spectrometry) log is used to identify formation clay minerals that is an indicator of three radioactive elements thorium, uranium and potassium and the amount of each of these elements and according to amount of each of these elements and their ratio gives a description of clay minerals of each zone. CGR log represents the sum of two elements Thorium and potassium that are present in the shale and uranium has no effect on it. The CGR log is usually used as a shale indicator and it is an essential tool for determining the Shale volume in well logging operation. In this study the relationship between shale volume shown by the CGR log and the type of formation clay mineral was investigated. A very clear relationship between the shale volume and formation clay minerals was observed. In intervals with low shale volume the amount of active clay minerals, especially montmorillonite was higher and in intervals with high shale volume, inactive clay minerals were more. In order to investigate the spatial relation between the logging data, frequency distribution and correlation between logging data was studied. By using logging data and identifying the type of clay minerals in each zone and also the spatial correlation between logging data a suitable program for drilling and exploitation of oil fields in different areas can be proposed

Analysis of deep stress field using well log and wellbore breakout data: a case study in Cretaceous oil reservoir, southwest Iran

To identify the wellbore instability of Bangestan oil reservoir in the southwestern Iran, the direction and magnitude of stresses were determined using two different methods in this study. Results of injection test and analysis of wellbore breakouts were used to verify the accuracy of the stress profiles. In this study the Bartoon method, which using the breakout angle and strength of rock, was used. In addition, the ability of artificial neural network to estimate the elastic parameters of rock and stress field was used. The output of the neural network represents a high accuracy in the estimation of the desired parameters. In addition, the Mohr-Coulomb failure criterion was used to verify stress profiles. Estimated stresses show relative compliance with the results of injection test and Barton method. The required minimum mud pressure for preventing shear failures was calculated by using the Mohr-Coulomb failure criterion and the estimated stress profiles. The results showed a good compliance with failures which have been identified in the caliper and image logs. However, a number of noncompliance is observed in some depth. This is due to the concentration of fractures, collisions between the drill string and the wellbore wall, as well as swab and surge pressures. The stress mode is normal and strike-slip in some depth based on the estimated stress profiles. According to direction of breakouts which is clearly visible in the caliper and image logs, the minimum and maximum horizontal stresses directions were NW-SE and NE-SW, respectively. Thses directions were consistent with the direction of regional stresses in the Zagros belt

Estimation of the fracture density in reservoir rock using regression analysis of the petrophysical data

Image logs are presently the main specialized tools for fracture detection in hydrocarbon reservoirs. Where image logs are not available, other less rewarding substitutes such as isolated well tests and type curve analysis, drilling mud loss history, core description and conventional petrophysical logs are used for fracture detection. In this paper a novel method is proposed for fracture density estimation in the fractured zones, using energy of petrophysical logs. Image and petrophysical logs from Asmari reservoir in one well of an oilfield in southwestern Iran were used to investigate the accuracy and applicability of the proposed method. Energy of the petrophysical logs in the fractured zones is calculated and linear and non-linear regressions between them are estimated. Results show that there is strong correlation between the energy of caliper, sonic (DT), density (RHOB) and lithology (PEF) logs with fracture density in well. In order to find a generalized estimator, a unique normalization method are developed, and by using it, a non-linear regression has been found which estimates fracture density with correlation coefficient of higher than 85%. The resultant regression has the capability of generalization in the studied field

Study of dependence between clay mineral distribution and shale volume in reservoir rocks using geostatistical and petrophysical methods

Identify and obtain a detailed understanding of shale and its clay minerals in three segments; exploration, drilling and reservoir in the oil industry are very important. The study of the formation clay minerals in terms of depth and layers of earth is done through X-ray tests on samples taken from the reservoir which in comparison with logging requires a lot more time and cost and also can't provide continuous results because continuous sampling from the whole well is not possible. NGS (Gamma-ray Spectrometry) log is used to identify formation clay minerals that is an indicator of three radioactive elements thorium, uranium and potassium and the amount of each of these elements and according to amount of each of these elements and their ratio gives a description of clay minerals of each zone. CGR log represents the sum of two elements Thorium and potassium that are present in the shale and uranium has no effect on it. The CGR log is usually used as a shale indicator and it is an essential tool for determining the Shale volume in well logging operation. In this study the relationship between shale volume shown by the CGR log and the type of formation clay mineral was investigated. A very clear relationship between the shale volume and formation clay minerals was observed. In intervals with low shale volume the amount of active clay minerals, especially montmorillonite was higher and in intervals with high shale volume, inactive clay minerals were more. In order to investigate the spatial relation between the logging data, frequency distribution and correlation between logging data was studied. By using logging data and identifying the type of clay minerals in each zone and also the spatial correlation between logging data a suitable program for drilling and exploitation of oil fields in different areas can be proposed

A geostatistical approach for predicting the top producing formation in oil fields

Drilling engineer's understanding of the subsurface conditions of oil-rich regions in Iran is based on experience and through quantitative assessment of these valuable data. The usage of geostatistical methods converts the qualitative experience to quantitative and provides the way for better result. In Iranian oil fields, during the drilling operation Asmari formation is of great importance because most of oil reservoirs are located in this formation. In this study, 53 wells in the field were randomly selected, and after studying and reviewing the drilling and geological reports, 40 wells were selected for inclusion in the model. After analysis of the information, a model which predicts the top of Producing Formation accurately was presented

Streamlining Digital Modeling and Building Information Modelling (BIM) Uses for the Oil and Gas Projects

The oil and gas industry is a technology-driven industry. Over the last two decades, it has heavily made use of digital modeling and associated technologies (DMAT) to enhance its commercial capability. Meanwhile, the Building Information Modelling (BIM) has grown at an exponential rate in the built environment sector. It is not only a digital representation of physical and functional characteristics of a facility, but it has also made an impact on the management processes of building project lifecycle. It is apparent that there are many similarities between BIM and DMAT usability in the aspect of physical modeling and functionality. The aim of this study is to streamline the usage of both DMAT and BIM whilst discovering valuable practices for performance improvement in the oil and gas projects. To achieve this, 28 BIM guidelines, 83 DMAT academic publications and 101 DMAT vendor case studies were selected for review. The findings uncover (a) 38 BIM uses; (b) 32 DMAT uses and; (c) 36 both DMAT and BIM uses. The synergy between DMAT and BIM uses would render insightful references into managing efficient oil and gas’s projects. It also helps project stakeholders to recognise future investment or potential development areas of BIM and DMAT uses in their projects

Application of concentration-area fractal method in static modeling of hydrocarbon reservoirs

Abstract Separating and identifying various fractal communities are the most crucial steps in static reservoir modeling. There are different ways for the identification and separation which vary from simple statistical methods (on the basis of statistical parameters functions Function) to complicated fractal methods (on the basis of the spatial structure of data). Fractal geometry supplies new instruments to estimate hydrocarbon reservoir properties. In the last few years, fractal geometry is known as a new trick of human mind for identifying and analyzing behavioral and structural complexities of generally natural phenomena. One of the uses of fractal geometry is to estimate the threshold limit and the results of separating the anomaly communities from the base regarding the fractal dimension differences. In this study, after saturation parameter modeling of a reservoir rock located in south of Iran, different communities were separated by kriging geostatistical method and using concentration-area fractal method. Based on the water saturation parameters, the results of fractal analysis represent two different communities in the reservoir

Establishment of tensile failure induced sanding onset prediction model for cased-perforated gas wells

Sand production is a challenging issue in upstream oil and gas industry, causing operational and safety problems. Therefore, before drilling the wells, it is essential to predict and evaluate sanding onset of the wells. In this paper, new poroelastoplastic stress solutions around the perforation tunnel and tip based on the Mohr–Coulomb criterion are presented firstly. Based on the stress models, a tensile failure induced sanding onset prediction model for cased-perforated gas wells is derived. Then the analytical model is applied to field data to verify its applicability. The results from the perforation tip tensile failure induced sanding model are very close to field data. Therefore, this model is recommended for forecasting the critical conditions of sand production analysis. Such predictions are necessary for providing technical support for sand control decision-making and predicting the production condition at which sanding onset occurs