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Results
Abstract Past drilling of vertical and moderately deviated development wells in offshore Peninsular Malaysia and Vietnam has proven to be challenging. Drilling experience in the development wells highlighted the issue of wellbore instability in the respective areas, particularly though coal seams. Numerous lost-time incidents related to wellbore instability-related problems were experienced, ranging from tight hole (remedied by reaming) to overpull, pack-off followed by stuck pipe, fill on-bottom to difficulties in running casing, and coal cavings to high gas associated with drilling breaks. These problems were observed particularly when drilling through the weak shales with interbedded unstable coals. Coal instability often does not respond to the same remediation used in shale, where we usually simply raise the mud weight to reduce the compressional hoop stress below the strength of the rock. Borehole collapse or breakout may still occur when the coal cleats and natural fractures allow the drilling fluid filtrate to invade despite using an optimum mud weight. This results in pressurization of the near-wellbore region and loss of effective mud weight support for coal stability. All the wells in the respective areas were drilled with WBM and so drilling performance benchmarking with other drilling fluids was not possible in the study area. Faced with continual NPT, a geomechanical study was initiated to mitigate the coal related wellbore instability problems. The recommendations arising from the comprehensive geomechanical and drilling experience analyses have been implemented to improve performance during subsequent development drilling. This paper highlights the importance of integrating geomechanics with proper drilling practices when developing strategies to mitigate unstable hole problems, especially related to coals. A full-scale geomechanical model was developed, validated and updated using logs and drilling data from wells in both the areas. The drilling experiences, rock mechanical properties, in-situ stresses and formation pressure in both the areas are presented and discussed in detail. A detailed recommendation on the drilling strategy through coal and the associated uncertainties was implemented. Utilization of geomechanical results from the two studies and the approach adopted in the development of drilling strategies helped to determine recommended optimal mud weight programs for the future wells. Subsequent drilling campaigns have all been successful by incorporation of the entire risk and mitigation plan. This included a generalized road map with a protocol for drilling through coal, tripping and back reaming during drilling, pre-drilling and post-drilling. This effort, together with optimized drilling fluid design and the correct mud weight based on previous drilling experience as per recommended wellbore stability assessments, helped in two recently drilled wells in different areas with reduced NPT.
- North America > United States (0.93)
- Asia > Vietnam (0.61)
- Asia > Malaysia (0.61)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (0.88)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.45)
Foam Diversion in Heterogeneous Reservoirs: Effect of Permeability and Injection Method
Al Ayesh, A. H. (Delft University of Technology and Saudi Aramco) | Salazar, R.. (Delft University of Technology) | Farajzadeh, R.. (Delft University of Technology and Shell Global Solutions International) | Vincent-Bonnieu, S.. (Delft University of Technology and Shell Global Solutions International) | Rossen, W. R. (Delft University of Technology)
Summary Foam can divert flow from higher- to lower-permeability layers and thereby improve the injection profile in gas-injection enhanced oil recovery (EOR). This paper compares two methods of foam injection, surfactant-alternating-gas (SAG) and coinjection of gas and surfactant solution, in their abilities to improve injection profiles in heterogeneous reservoirs. We examine the effects of these two injection methods on diversion by use of fractional-flow modeling. The foam-model parameters for four sandstone formations ranging in permeability from 6 to 1,900 md presented by Kapetas et al. (2015) are used to represent a hypothetical reservoir containing four noncommunicating layers. Permeability affects both the mobility reduction of wet foam in the low-quality-foam regime and the limiting capillary pressure at which foam collapses. The effectiveness of diversion varies greatly with the injection method. In a SAG process, diversion of the first slug of gas depends on foam behavior at very-high foam quality. Mobility in the foam bank during gas injection depends on the nature of a shock front that bypasses most foam qualities usually studied in the laboratory. The foam with the lowest mobility at fixed foam quality does not necessarily give the lowest mobility in a SAG process. In particular, diversion in SAG depends on how and whether foam collapses at low water saturation; this property varies greatly among the foams reported by Kapetas et al. (2015). Moreover, diversion depends on the size of the surfactant slug received by each layer before gas injection. This favors diversion away from high-permeability layers that receive a large surfactant slug. However, there is an optimum surfactant-slug size: Too little surfactant and diversion from high-permeability layers is not effective, whereas with too much, mobility is reduced in low-permeability layers. For a SAG process, injectivity and diversion depend critically on whether foam collapses completely at irreducible water saturation. In addition, we show the diversion expected in a foam-injection process as a function of foam quality. The faster propagation of surfactant and foam in the higher-permeability layers aids in diversion, as expected. This depends on foam quality and non-Newtonian foam mobility and varies with injection time. Injectivity is extremely poor with foam injection for these extremely strong foams, but for some SAG foam processes with effective diversion it is better than injectivity in a waterflood.
- Europe (1.00)
- Asia > Middle East (0.67)
- North America > United States > Texas (0.67)
- South America > Colombia > Casanare Department > Llanos Basin > Cusiana Field > Mirador Formation (0.99)
- North America > United States > Texas > Permian Basin > Salt Creek Field (0.99)
- Europe > Norway > North Sea > Northern North Sea > East Shetland Basin > PL 375 > Block 34/7 > Snorre Field > Statfjord Group (0.99)
- (15 more...)
Three digital earth models were designed and constructed during SEAM Phase II to study exploration challenges at the scale of modern land seismic surveys. Although built as generic models, each was based on one or more related geologic type areas. The Barrett model represents the seismic anisotropy of complex laminated and fractured shale reservoirs, based on the Woodford and Eagle Ford formations and set below a stratigraphic overburden and near surface of a North American midcontinent basin. The Arid model features the extreme property contrasts of desert terrains in a 500 m thick near surface that juxtaposes hard carbonate bedrock and soft sediments filling karsts, typical of the Saudi Arabian Peninsula. The Foothills model contains sharp surface topography and alluvial fan-like sediments above complex fold-and-thrust structures based on the compressive tectonics of the Llanos Foothills of South America. All three models were built in workflows that combined automated steps with a large measure of manual model building, which represents the current state of the art in geologic modeling for large-scale geophysical simulations. The Barrett and Arid models each contain about 1.5 billion grid cells representing regions 10 × 10 × 3.75 km in physical size. The Foothills model has about 2 billion cells representing a region about 14.5 × 12.5 × 11 km. Full elastic-wave simulations with these models were run for a combined total of about 170,000 shots, usually with millions of recorded channels per shot, generating several petabytes of seismic data in standard and novel shot-receiver geometries. Selected shots from these simulations show that large, detailed earth models can reproduce features of land seismic surveys that continue to challenge the best modern seismic data processing and imaging techniques.
- North America > United States > Texas (1.00)
- Asia (1.00)
- Research Report > Strength Medium (0.54)
- Research Report > Experimental Study (0.54)
- Geology > Structural Geology > Tectonics (1.00)
- Geology > Geological Subdiscipline > Stratigraphy (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.73)
- South America > Colombia > Casanare Department > Llanos Basin > Cusiana Field > Mirador Formation (0.99)
- North America > United States > Oklahoma > Arkoma Basin > Cana Woodford Shale Formation (0.99)
- North America > United States > Arkansas > Arkoma Basin > Cana Woodford Shale Formation (0.99)
- (25 more...)
Abstract Interpreting land seismic data in the Colombian Foothills poses many challenges. Very often, the data have a low signal-to-noise ratio and the subsurface prospective structures are significantly complex. The level of uncertainty can be so high that even experienced interpreters struggle to reconcile the seismic image with their geologic models. Based on previous knowledge and “fast-track” interpretation of old 2D prestack time migration data (no 3D seismic in the area), we identified two interesting plays for further analysis: a triangular zone (play 1) and subthrust anticlines beneath the frontal fault (play 2). Derisking the different prospects associated with plays 1 and 2 required the application of prestack depth migration (PSDM), which reduce uncertainty regarding the position of the structures, their depth, and even their existence. The seismic image in play 1 structures was improved significantly with better definition of the flanks of the anticlines and the frontal closure of the structures, more coherent events, and sharper definition in fault cut-offs. Some apparent play 2 prospects, that were actually “velocity pull-up” anticlines, were corrected by the depth-migration workflow, whereas other structures experience important modifications in their geometry. In both types of plays, depth migration dramatically changed the initial assessment of prospectivity. Based on the better agreement between seismic and borehole data, significant reduction in residual moveout on final PSDM gathers and more coherent seismic images, we believe that the use of depth migration has allowed us to obtain a more accurate representation of the subsurface, and consequently a more rigorous reserves estimation. The use of PSDM was essential to understand the complexities in the prospects evaluated and the risk associated with their exploration. We consider the lessons learned in this study applicable to similar geologic environments worldwide.
- South America > Colombia (1.00)
- North America > United States > Texas (0.28)
- Geology > Geological Subdiscipline (0.94)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (0.78)
- South America > Colombia > Meta Department > Llanos Basin > Cano Sur Block > Carbonera Formation (0.99)
- South America > Colombia > Llanos Basin > Gacheta Formation (0.99)
- South America > Colombia > Casanare Department > Llanos Basin > Cusiana Field > Mirador Formation (0.99)
- (11 more...)
ABSTRACT: This paper presents a novel study on geomechanics of fluid injection from a fully penetrating vertical wellbore into a weakly consolidated formation confined with soft rocks. For the first time, impacts of vertical confinement are incorporated to evaluate: flow-induced poro-elasto-plastic stresses, failure mechanism/s, and failure planes. A new fully-coupled numerical model is developed where the response of the injection layer in the plane perpendicular to injection flow is simulated through adopting “interface” – a plane on which sliding or separation can occur – analogous to the Winkler model. An assessment of pore pressures, stresses, and failure planes confirms two types of induced behaviors: dilation in the well vicinity; and compaction, a main cause of physical clogging which impacts competence of the operation. Numerical results describe multiple distinct zones evolving with time around the injection well: (1) liquefied domain, (2) multiple plastic domains, (3) elastic region. Inner plastic domains are prone to occur.
ABSTRACT Past drilling of vertical and moderately deviated development wells in offshore Peninsular Malaysia and offshore Vietnam has proven to be challenging. Drilling experience in the development wells highlighted the issue of wellbore instability in the respective study areas, particularly though coal seams. Numerous lost-time incidents related to wellbore instability-related problems were experienced, ranging from tight hole (remedied by reaming) to overpull, pack-off followed by stuck pipe, fill on-bottom to difficulties in running casing, and coal cavings to high gas associated with drilling breaks. These problems were observed particularly when drilling through the weak shales with interbedded unstable coals. Coal instability often does not respond to the same remediation used in shale, where we usually simply raise the mud weight to reduce the compressional hoop stress below the strength of the rock. Borehole collapse or breakout may still occur when the coal cleats and natural fractures of the coal allow the drilling fluid filtrate to invade despite using an optimum mud weight. This results in pressurization of the near-wellbore region and loss of effective mud weight support for coal stability. All the wells in the respective fields were drilled with water-based mud (WBM) and so drilling performance benchmarking with other drilling fluids was not possible in the study area. Faced with continual non-productive time (NPT), a geomechanical study was initiated to mitigate the wellbore instability problems. The recommendations arising from the comprehensive geomechanical and drilling experience analyses have been implemented to improve performance during subsequent development drilling. This paper highlights the importance of integrating geomechanics with proper drilling practices when developing strategies to mitigate unstable hole problems, especially related to coals. A full-scale geomechanical model was developed, validated and updated using logs and drilling data from wells in both the areas. The drilling experiences, rock mechanical properties, in-situ stresses and formation pressure in both the study areas are presented and discussed in detail. A detailed recommendation on the drilling strategy through coal and the associated uncertainties was implemented. Utilization of geomechanical results from the two studies and the approach adopted in the development of drilling strategies helped to determine recommended optimal mud weight programs for the future wells. Subsequent drilling campaigns have all been successful by incorporation of the entire risk and mitigation plan. This included a generalized road map with a protocol for drilling through coal, tripping and back reaming during drilling, pre-drilling and post-drilling. This effort, together with optimized drilling fluid design and the correct mud weight based on previous drilling experience as per recommended wellbore stability assessments, helped in two recently drilled wells in different areas with reduced non-productive time.
- Asia (1.00)
- North America > United States > Texas (0.28)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.45)
Summary The ability of foam to divert gas flow during a long period of gas injection in a surfactant-alternating-gas (SAG) foam process is important for the economics of foam-diversion processes for enhanced oil recovery (EOR). Here, we interpret field data from the foam test in the Cusiana field in Colombia (Ocampo et al. 2013). In this test, surfactant was injected into a single layer that had been taking approximately half the injected gas before the test; then, gas injection resumed into all layers. On the basis of the size of the surfactant slug injected and estimates of adsorption and of water saturation in the foam in situ, we estimate that the treated region extended approximately 5.3 m from the injection well; fortunately, the results to follow are not sensitive to this estimate. On the basis of the change in injection logs before the test and at Day 5 of the test, when approximately 30 pore volumes (PVs) of gas (relative to the volume of the treated zone) had been injected, foam still reduced gas mobility in the treated layer to approximately 11% of its pretrial value. We base this estimate on the decrease of injection into the treated layer and the increase of injection into the other layers; the results are consistent among the layers. After 35 and 152 days of injection (220 and 1,250 treatment PV of gas injected), foam reduced gas mobility in the treated zone to approximately 26 and 50% of its value before the test, respectively. This result indicates that foam continued to reduce mobility by a modest amount even after long injection of gas. On the other hand, foam did weaken progressively as it dried out. Foam models in which foam remains strong at irreducible water saturation would greatly overestimate foam effectiveness at long times in this test. In this test, the large volume of gas had quickly penetrated far beyond the edge of the surfactant bank. Mobility in the foam-treated region in this test, after passage of many treatment PVs of gas injection, mimics that very near the injection well in a process with a larger slug of surfactant.
- Europe (1.00)
- North America > United States (0.93)
- South America > Colombia > Casanare Department (0.25)
- South America > Colombia > Mirador Formation (0.99)
- South America > Colombia > Casanare Department > Llanos Basin > Cusiana Field > Mirador Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > East Shetland Basin > PL 375 > Block 34/7 > Snorre Field > Statfjord Group (0.99)
- (12 more...)
Foam Diversion in Heterogeneous Reservoirs: Effect of Permeability and Injection Method
Al Ayesh, A. H. (Department of Geoscience and Engineering, Delft University of Technology) | Salazar, R.. (Department of Geoscience and Engineering, Delft University of Technology) | Farajzadeh, R.. (Department of Geoscience and Engineering, Delft University of Technology) | Vincent-Bonnieu, S.. (Department of Geoscience and Engineering, Delft University of Technology) | Rossen, W. R. (Department of Geoscience and Engineering, Delft University of Technology)
Abstract Foam can divert flow from higherto lower-permeability layers and thereby improve vertical conformance in gas-injection enhanced oil recovery. Recently, Kapetas et al. (2015) measured foam properties in cores from four sandstone formations ranging in permeability from 6 to 1900 md, and presented parameter values for foam model fit to those data. Permeability affects both the mobility reduction of wet foam in the "low-quality" foam regime and the limiting capillary pressure at which foam collapses. Kapetas et al. showed how foam would divert injection between layers of these formations if all layers were full of foam injected at a given quality (gas fractional flow). Here we examine the effects of injection method on diversion in a dynamic foam process using fractional-flow modeling and the model parameters derived by Kapetas et al. Like them, we consider a hypothetical reservoir containing non-communicating layers with the properties of the four formations in their study. The effectiveness of diversion varies greatly with injection method. In a SAG (surfactant-alternating-gas) process, diversion of the first slug of gas depends on foam behavior at very high foam quality. Mobility in the foam bank during gas injection depends on the nature of a shock front that bypasses most foam qualities usually studied in the laboratory. The foam with the lowest mobility at fixed foam quality does not necessarily give the lowest mobility in a SAG process. In particular, diversion in SAG depends on how and whether foam collapses at low water saturation; this property varies greatly among the foams reported by Kapetas et al. Moreover, diversion depends on the size of the surfactant slug received by each layer before gas injection. This of course favors diversion away from high-permeability layers that receive a large surfactant slug, but there is an optimum surfactant slug size: too little surfactant and diversion from high-permeability layers is not effective; too much and mobility is reduced in low-permeability layers, too. For a SAG process, it is very important to determine if foam collapses completely at irreducible water saturation. In addition, we show the diversion expected in a foam-injection process as a function of foam quality. The faster propagation of surfactant and foam in the higher-permeability layers aids in diversion, as expected. This depends on foam quality and non-Newtonian foam mobility and varies with time of injection. Injectivity is extremely poor with foam injection, but is not necessarily worse than waterflood in some effective SAG foam processes
- Europe (1.00)
- North America > United States > Texas (0.93)
- Asia (0.67)
- South America > Colombia > Casanare Department > Llanos Basin > Cusiana Field > Mirador Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > East Shetland Basin > PL 375 > Block 34/7 > Snorre Field > Statfjord Group (0.99)
- Europe > Norway > North Sea > Northern North Sea > East Shetland Basin > PL 375 > Block 34/7 > Snorre Field > Lunde Formation (0.99)
- (15 more...)
Movement vectors and deformation mechanisms in kinematic restorations: A case study from the Colombian Eastern Cordillera
Carrillo, Emilio (Instituto Colombiano del Petróleo-Ecopetrol) | Mora, Andrés (Instituto Colombiano del Petróleo-Ecopetrol) | Ketcham, Richard A. (University of Texas at Austin) | Amorocho, Ricardo (Instituto Colombiano del Petróleo-Ecopetrol) | Parra, Mauricio (University of São Paulo, Cidade Universitaria) | Costantino, Diego (Instituto Colombiano del Petróleo-Ecopetrol) | Robles, Wilmer (Instituto Colombiano del Petróleo-Ecopetrol) | Avellaneda, William (Instituto Colombiano del Petróleo-Ecopetrol) | Carvajal, Juan S. (Instituto Colombiano del Petróleo-Ecopetrol) | Corcione, Miguel F. (Instituto Colombiano del Petróleo-Ecopetrol) | Bello, Wladimir (Instituto Colombiano del Petróleo-Ecopetrol) | Figueroa, Juan D. (Instituto Colombiano del Petróleo-Ecopetrol) | Gómez, José F. (Instituto Colombiano del Petróleo-Ecopetrol) | González, José L. (Instituto Colombiano del Petróleo-Ecopetrol) | Quandt, Dennis (Instituto Colombiano del Petróleo-Ecopetrol) | Reyes, Martín (Instituto Colombiano del Petróleo-Ecopetrol) | Rangel, Ana M. (Instituto Colombiano del Petróleo-Ecopetrol) | Román, Ignacio (Instituto Colombiano del Petróleo-Ecopetrol) | Pelayo, Yasmin (Instituto Colombiano del Petróleo-Ecopetrol) | Porras, José (Instituto Colombiano del Petróleo-Ecopetrol)
Abstract We have developed a new method to assess the movement of particles in different steps of a well-calibrated sequential kinematic restoration. Calibration included correct assessment of amounts of overburden, sedimentation, erosion, and thermal behavior through time. Our method allowed a better understanding of the mechanisms of deformation and uplift in different geologic provinces. In our pilot case study in the Colombian Eastern Cordillera, we have used movement vectors in balanced cross sections to document an initial phase of dominant vertical uplift and a final phase of dominant tangential horizontal shortening. Our findings challenged the common assumptions related to folding and deformation mechanisms in fold-and-thrust belts used for cross-section balancing and palinspastic reconstructions. Thus, we found that the movement vectors in cross sections can be used to test and validate a complete procedure to obtain calibrated sequential kinematic restorations and represent a powerful tool to better understand deformation mechanisms in different settings.
- Europe (0.68)
- South America > Colombia > Santander Department (0.28)
- North America > United States > Texas > Travis County > Austin (0.28)
- Overview > Innovation (0.48)
- Research Report > New Finding (0.48)
- Phanerozoic > Cenozoic > Neogene > Miocene (0.70)
- Phanerozoic > Mesozoic (0.69)
- Phanerozoic > Cenozoic > Paleogene (0.68)
- Geology > Structural Geology > Tectonics > Plate Tectonics (1.00)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (1.00)
- Geology > Structural Geology > Fault (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- South America > Colombia > Tolima Department > Middle Magdalena Basin > Casabe Field (0.99)
- South America > Colombia > Santander Department > Middle Magdalena Basin > Casabe Field (0.99)
- South America > Colombia > Llanos Basin > Une Formation (0.99)
- (8 more...)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Geologic modeling (1.00)
- (4 more...)
Influence of salt in the tectonic development of the frontal thrust belt of the eastern Cordillera (Guatiquía area, Colombian Andes)
Parravano, Vanessa (Universitat Autònoma de Barcelona, SGS Horizon) | Teixell, Antonio (Universitat Autònoma de Barcelona) | Mora, Andrés (Instituto Colombiano del Petróleo-Ecopetrol)
Abstract Geologic maps, seismic lines, and data from a dry exploration well were used to develop a new structural model for a segment of the eastern foothills of the Eastern Cordillera of Colombia, emphasizing the role of salt tectonics. Milestones in the deformation history of the Guatiquía foothills were studied by sequential section restoration to selected steps. Uncommon structural geometries and sparse salt occurrences were interpreted in terms of a kinematic evolution in which Cretaceous salt migration in extension produced a diapiric salt wall, which was subsequently welded during the main episodes of the Andean compression, when the salt wall was squeezed generating a large overturned flap. Salt-weld strain hardening resulted in breakthrough thrusting across the overturned flap in late deformation stages. We have evaluated a pattern of salt tectonics previously unrecognized in the foothills thrust belt, which may be significant in other parts of the external Colombian Andes.
- South America > Colombia (1.00)
- Europe (1.00)
- North America > United States (0.93)
- Phanerozoic > Mesozoic > Cretaceous > Lower Cretaceous (1.00)
- Phanerozoic > Cenozoic > Paleogene (1.00)
- Phanerozoic > Cenozoic > Neogene (0.94)
- Phanerozoic > Mesozoic > Cretaceous > Upper Cretaceous > Campanian (0.46)
- Geology > Structural Geology > Tectonics > Salt Tectonics (1.00)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Metals & Mining (0.93)
- South America > Colombia > Mirador Formation (0.99)
- South America > Colombia > Llanos Basin (0.99)
- South America > Colombia > Casanare Department > Llanos Basin > Cusiana Field > Mirador Formation (0.99)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Geologic modeling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)