Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology h... more Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology have been combined to yield powerful new insights to reservoir tar mats. The asphaltene nanoscience model, the modified Yen model, also known as the Yen-Mullins model, has enabled development of the industry's first predictive equation of state for asphaltene concentration gradients. This equation of state (EOS) is a modified Flory-Huggins regular solution model for the asphaltene part that has been referred to as the Flory-Huggins-Zuo (FHZ) EOS for asphaltene concentration gradients in oil reservoirs. Measurement of these gradients using "downhole fluid analysis" coupled with analysis using the FHZ EOS has successfully addressed a variety of reservoir concerns including reservoir connectivity, viscosity gradients, and fluid disequilibrium. The EOS model shows that asphaltene concentration gradients can be large owing to both the gravity term and gas/oil ratio (GOR) gradients. The FHZ EOS is reduced to a very simple formthe gravity term only for low GOR black oils and heavy oilsand heavy oils are shown to exhibit enormous asphaltene concentration gradients in contrast to predictions from conventional models. In this paper, the FHZ EOS has been applied not only to calculate asphaltene concentration gradients but also to predict asphaltene phase instability in oil reservoirs. Two types of tar mats are discussed: one with a large discontinuous increase in asphaltene concentration versus depth typically at the base of an oil column (corresponding to asphaltene phase transition); the second with a continuous increase in asphaltene content at the base of a heavy oil column due to an exponential increase in viscosity with asphaltene content. Both types of tar mats are consistent with the Yen-Mullins model of asphaltenes within the FHZ EOS analysis discussed herein. The predictions are in good agreement with the laboratory and field observations, and the mechanisms of forming these two kinds of tar mats are also discussed. This methodology establishes a powerful new approach for conducting the analyses of asphaltene concentration grading and tar mat formation in oil reservoirs by integrating the Yen-Mullins model and the FHZ EOS with DFA technology.
Optimized geomodeling and history matching of production data is presented by utilizing an integr... more Optimized geomodeling and history matching of production data is presented by utilizing an integrated rock and fluid workflow. Facies identification is performed by use of image logs and other geological information. In addition, image logs are used to help define structural geodynamic processes that occurred in the reservoir. Methods of reservoir fluid geodynamics are used to assess the extent of fluid compositional equilibrium, especially the asphaltenes, and thereby the extent of connectivity in these facies. Geochemical determinations are shown to be consistent with measurements of compositional thermodynamic equilibrium. The ability to develop the geo-scenario of the reservoir, the coherent evolution of rock and contained fluids in the reservoir over geologic time, improves the robustness of the geomodel. In particular, the sequence of oil charge, compositional equilibrium, fault block throw, and primary biogenic gas charge are established in this middle Pliocene reservoir with...
SPE Annual Technical Conference and Exhibition, 2020
Hydrocarbon identification and evaluation with conventional triple-combo logs and Archie-based eq... more Hydrocarbon identification and evaluation with conventional triple-combo logs and Archie-based equations in freshwater environments has been a challenge for petrophysicists. In the first case study from Alaska, shallow reservoir information from non-Archie based technologies including total organic carbon (TOC) from spectroscopy measurements, hydrocarbon volume derived from dielectric and NMR logs were used for quick hydrocarbon bearing zones identification, decision making on fluid sampling and early determination of oil properties. The high-resolution NMR T1-T2 maps, derived from the latest inversion, revealed the presence of viscous oil. Another targeted formation is a laminated shaly sand sequence, also in a freshwater environment. The array resistivity logs show a low contrast profile and it is more challenging for fluid identification and evaluation. Relatively high resistivity anisotropy from 3D induction suggest the formation is potentially hydrocarbon bearing. TOC from spec...
Deepwater fields, such as those encountered in the Gulf of Mexico (GoM), often exhibit reservoir ... more Deepwater fields, such as those encountered in the Gulf of Mexico (GoM), often exhibit reservoir tar deposits and asphaltene instability (Dumont et al, 2012, Mullins et al, 2016). This instability may manifest itself within the reservoir in the form of out of equilibrium asphaltene gradients and tar deposits. These tar deposits can present drilling hazards which are a major nuisance for drilling operations, and can force operators to drill multiple sidetracks or bypass wells. This of course leads to increase well spend and rig time usage. For instance, the last two years showed that approximately 5% of the wells drilled in the GoM encountered severe drilling issues related to asphaltenes/tar deposits. Even more critical and concerning, is that asphaltene instability can have major implications for field developments, stretching expenditure risks beyond a single well to that of an entire field. From a flow assurance point of view, comingling incompatible oil produced from different z...
The measurement of geomechanical properties of reservoir rock and caprock for completion optimiza... more The measurement of geomechanical properties of reservoir rock and caprock for completion optimization, enhanced oil recovery (EOR), and disposal/storage of any kind is becoming an integral and key aspect of asset evaluation and appraisal. One of the most important of these characteristics is an in-situ evaluation of the magnitude and variation of the minimum in-situ stress, the measurement of which is critical for geomechanical modelling and thereby a range of applications such as well construction, caprock integrity, and completion optimization. A wireline formation testing (WFT) tool is a common approach for obtaining direct measurements of these stresses at a range of depths. This process is referred to as microfracturing and is most typically performed in an openhole environment. Typical toolstrings consist of a straddle packer arrangement, a pumping mechanism, gamma ray for accurate depth correlation, a motorized valve/manifold arrangement, and pressure/temperature gauges. To p...
International Petroleum Technology Conference, 2013
Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology h... more Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology have been integrated to yield powerful new insights to reservoir dynamics. The Yen-Mullins model of asphaltene nanoscience has enabled development of the industry's first predictive equation of state (EOS) for asphaltene concentration gradients - the Flory-Huggins-Zuo (FHZ) EOS in oil reservoirs. The FHZ EOS along with DFA measurements has successfully addressed a variety of reservoir concerns including reservoir connectivity, viscosity gradients, and fluid disequilibrium. The model shows that asphaltene concentration gradients can be large owing to both the gravity term and gas/oil ratio (GOR) gradients. The FHZ EOS is reduced to a very simple form for low GOR black oils and heavy oils, and heavy oils are shown to exhibit enormous asphaltene concentration gradients compared to conventional black oil. In this paper, the FHZ EOS has been applied not only to calculate asphaltene concentration gradients but also to predict asphaltene phase instability in oil reservoirs and potential flow assurance issues. Two categories of tar mats are addressed, one with a large discontinuous increase in asphaltene concentration versus depth typically at the base of an oil column (corresponding to asphaltene phase transition); the second with a continuous increase in asphaltene content at the base of a mobile heavy oil column due to an exponential increase in viscosity with asphaltene content. The discontinuous type of tar mat is show to occur in two distinct setting, one more common tar mat at the base of the column and a second unusual tar mat that occurs upstructure and is permeable. The predictions are in good agreement with the laboratory and field data and the mechanisms of forming these two kinds of tar mats are also discussed. This methodology establishes a powerful new approach for conducting the analyses of asphaltene concentration grading, flow assurance and tar mat formation in oil reservoirs by integrating the Yen-Mullins model, and the FHZ EOS with DFA technology.
International Petroleum Technology Conference, 2007
The Casabe fi eld in the middle Magdalena valley of Colombia has been producing since the mid-194... more The Casabe fi eld in the middle Magdalena valley of Colombia has been producing since the mid-1940s. With some 18 million bbl remaining recoverable reserves, the fi eld is undergoing its third redevelopment campaign.
International Petroleum Technology Conference, 2009
Qatargas 3 and Qatargas 4 ventures are jointly developing their assigned project area of the Nort... more Qatargas 3 and Qatargas 4 ventures are jointly developing their assigned project area of the North Field offshore Qatar, the world’s largest non-associated natural gas field. The area allocated to the joint development is a 15km by 20.5 km block and consists of 3 15-slot platforms, each with 11 wells drilled into the Khuff carbonate reservoir. Currently the Qatargas 3&4 block is in its late development phase where over 75% of its wells have been drilled, evaluated and completed. The formation evaluation is generally carried out using data acquired by wireline conveyed tools and a standard log acquisition program consist of two runs configured to record mainly resistivity, porosity, sonic and formation pressure data.
Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology h... more Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology have been combined to yield powerful new insights to reservoir tar mats. The asphaltene nanoscience model, the modified Yen model, also known as the Yen-Mullins model, has enabled development of the industry's first predictive equation of state for asphaltene concentration gradients. This equation of state (EOS) is a modified Flory-Huggins regular solution model for the asphaltene part that has been referred to as the Flory-Huggins-Zuo (FHZ) EOS for asphaltene concentration gradients in oil reservoirs. Measurement of these gradients using "downhole fluid analysis" coupled with analysis using the FHZ EOS has successfully addressed a variety of reservoir concerns including reservoir connectivity, viscosity gradients, and fluid disequilibrium. The EOS model shows that asphaltene concentration gradients can be large owing to both the gravity term and gas/oil ratio (GOR) gradients. The FHZ EOS is reduced to a very simple formthe gravity term only for low GOR black oils and heavy oilsand heavy oils are shown to exhibit enormous asphaltene concentration gradients in contrast to predictions from conventional models. In this paper, the FHZ EOS has been applied not only to calculate asphaltene concentration gradients but also to predict asphaltene phase instability in oil reservoirs. Two types of tar mats are discussed: one with a large discontinuous increase in asphaltene concentration versus depth typically at the base of an oil column (corresponding to asphaltene phase transition); the second with a continuous increase in asphaltene content at the base of a heavy oil column due to an exponential increase in viscosity with asphaltene content. Both types of tar mats are consistent with the Yen-Mullins model of asphaltenes within the FHZ EOS analysis discussed herein. The predictions are in good agreement with the laboratory and field observations, and the mechanisms of forming these two kinds of tar mats are also discussed. This methodology establishes a powerful new approach for conducting the analyses of asphaltene concentration grading and tar mat formation in oil reservoirs by integrating the Yen-Mullins model and the FHZ EOS with DFA technology.
Optimized geomodeling and history matching of production data is presented by utilizing an integr... more Optimized geomodeling and history matching of production data is presented by utilizing an integrated rock and fluid workflow. Facies identification is performed by use of image logs and other geological information. In addition, image logs are used to help define structural geodynamic processes that occurred in the reservoir. Methods of reservoir fluid geodynamics are used to assess the extent of fluid compositional equilibrium, especially the asphaltenes, and thereby the extent of connectivity in these facies. Geochemical determinations are shown to be consistent with measurements of compositional thermodynamic equilibrium. The ability to develop the geo-scenario of the reservoir, the coherent evolution of rock and contained fluids in the reservoir over geologic time, improves the robustness of the geomodel. In particular, the sequence of oil charge, compositional equilibrium, fault block throw, and primary biogenic gas charge are established in this middle Pliocene reservoir with...
SPE Annual Technical Conference and Exhibition, 2020
Hydrocarbon identification and evaluation with conventional triple-combo logs and Archie-based eq... more Hydrocarbon identification and evaluation with conventional triple-combo logs and Archie-based equations in freshwater environments has been a challenge for petrophysicists. In the first case study from Alaska, shallow reservoir information from non-Archie based technologies including total organic carbon (TOC) from spectroscopy measurements, hydrocarbon volume derived from dielectric and NMR logs were used for quick hydrocarbon bearing zones identification, decision making on fluid sampling and early determination of oil properties. The high-resolution NMR T1-T2 maps, derived from the latest inversion, revealed the presence of viscous oil. Another targeted formation is a laminated shaly sand sequence, also in a freshwater environment. The array resistivity logs show a low contrast profile and it is more challenging for fluid identification and evaluation. Relatively high resistivity anisotropy from 3D induction suggest the formation is potentially hydrocarbon bearing. TOC from spec...
Deepwater fields, such as those encountered in the Gulf of Mexico (GoM), often exhibit reservoir ... more Deepwater fields, such as those encountered in the Gulf of Mexico (GoM), often exhibit reservoir tar deposits and asphaltene instability (Dumont et al, 2012, Mullins et al, 2016). This instability may manifest itself within the reservoir in the form of out of equilibrium asphaltene gradients and tar deposits. These tar deposits can present drilling hazards which are a major nuisance for drilling operations, and can force operators to drill multiple sidetracks or bypass wells. This of course leads to increase well spend and rig time usage. For instance, the last two years showed that approximately 5% of the wells drilled in the GoM encountered severe drilling issues related to asphaltenes/tar deposits. Even more critical and concerning, is that asphaltene instability can have major implications for field developments, stretching expenditure risks beyond a single well to that of an entire field. From a flow assurance point of view, comingling incompatible oil produced from different z...
The measurement of geomechanical properties of reservoir rock and caprock for completion optimiza... more The measurement of geomechanical properties of reservoir rock and caprock for completion optimization, enhanced oil recovery (EOR), and disposal/storage of any kind is becoming an integral and key aspect of asset evaluation and appraisal. One of the most important of these characteristics is an in-situ evaluation of the magnitude and variation of the minimum in-situ stress, the measurement of which is critical for geomechanical modelling and thereby a range of applications such as well construction, caprock integrity, and completion optimization. A wireline formation testing (WFT) tool is a common approach for obtaining direct measurements of these stresses at a range of depths. This process is referred to as microfracturing and is most typically performed in an openhole environment. Typical toolstrings consist of a straddle packer arrangement, a pumping mechanism, gamma ray for accurate depth correlation, a motorized valve/manifold arrangement, and pressure/temperature gauges. To p...
International Petroleum Technology Conference, 2013
Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology h... more Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology have been integrated to yield powerful new insights to reservoir dynamics. The Yen-Mullins model of asphaltene nanoscience has enabled development of the industry's first predictive equation of state (EOS) for asphaltene concentration gradients - the Flory-Huggins-Zuo (FHZ) EOS in oil reservoirs. The FHZ EOS along with DFA measurements has successfully addressed a variety of reservoir concerns including reservoir connectivity, viscosity gradients, and fluid disequilibrium. The model shows that asphaltene concentration gradients can be large owing to both the gravity term and gas/oil ratio (GOR) gradients. The FHZ EOS is reduced to a very simple form for low GOR black oils and heavy oils, and heavy oils are shown to exhibit enormous asphaltene concentration gradients compared to conventional black oil. In this paper, the FHZ EOS has been applied not only to calculate asphaltene concentration gradients but also to predict asphaltene phase instability in oil reservoirs and potential flow assurance issues. Two categories of tar mats are addressed, one with a large discontinuous increase in asphaltene concentration versus depth typically at the base of an oil column (corresponding to asphaltene phase transition); the second with a continuous increase in asphaltene content at the base of a mobile heavy oil column due to an exponential increase in viscosity with asphaltene content. The discontinuous type of tar mat is show to occur in two distinct setting, one more common tar mat at the base of the column and a second unusual tar mat that occurs upstructure and is permeable. The predictions are in good agreement with the laboratory and field data and the mechanisms of forming these two kinds of tar mats are also discussed. This methodology establishes a powerful new approach for conducting the analyses of asphaltene concentration grading, flow assurance and tar mat formation in oil reservoirs by integrating the Yen-Mullins model, and the FHZ EOS with DFA technology.
International Petroleum Technology Conference, 2007
The Casabe fi eld in the middle Magdalena valley of Colombia has been producing since the mid-194... more The Casabe fi eld in the middle Magdalena valley of Colombia has been producing since the mid-1940s. With some 18 million bbl remaining recoverable reserves, the fi eld is undergoing its third redevelopment campaign.
International Petroleum Technology Conference, 2009
Qatargas 3 and Qatargas 4 ventures are jointly developing their assigned project area of the Nort... more Qatargas 3 and Qatargas 4 ventures are jointly developing their assigned project area of the North Field offshore Qatar, the world’s largest non-associated natural gas field. The area allocated to the joint development is a 15km by 20.5 km block and consists of 3 15-slot platforms, each with 11 wells drilled into the Khuff carbonate reservoir. Currently the Qatargas 3&4 block is in its late development phase where over 75% of its wells have been drilled, evaluated and completed. The formation evaluation is generally carried out using data acquired by wireline conveyed tools and a standard log acquisition program consist of two runs configured to record mainly resistivity, porosity, sonic and formation pressure data.
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