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Africa (Sub-Sahara) United Hydrocarbon International finished drilling the Belanga North-1 exploration well located in Doba basin in southern Chad. The well was drilled to a total depth of 1392 m, and encountered three oil-bearing sand intervals--two in the targeted Upper Cretaceous "YO" sands and one in an untested shallower sand. United Hydrocarbon (100%) is the operator. Asia Pacific China National Offshore Oil Corporation discovered natural gas in the Qiongdongan basin, South China Sea. Well Lingshui 17-2--located in the east Lingshui sag portion of the basin at an average water depth of 1450 m--was drilled and completed to a depth of 3510 m. Lingshui 17-2 encountered a gas reservoir with a total thickness of approximately 55 m. Statoil Australia Theta has drilled and completed the Oz-Alpha 1 exploration well in the southern Georgina basin in the Northern Territory, Australia.
Africa (Sub-Sahara) United Hydrocarbon International finished drilling the Belanga North-1 exploration well located in Doba basin in southern Chad. The well was drilled to a total depth of 1392 m, and encountered three oil-bearing sand intervals--two in the targeted Upper Cretaceous "YO" sands and one in an untested shallower sand. United Hydrocarbon (100%) is the operator. Asia Pacific China National Offshore Oil Corporation discovered natural gas in the Qiongdongan basin, South China Sea. Well Lingshui 17-2--located in the east Lingshui sag portion of the basin at an average water depth of 1450 m--was drilled and completed to a depth of 3510 m. Lingshui 17-2 encountered a gas reservoir with a total thickness of approximately 55 m. Senex commenced a four-zone selective completion of its Sprigg-1 exploration well within the Murta and Tinchoo formations and also in the Hutton sandstone and Paning member.
Vargas Grajales, Viviana (Pontifical Catholic University of Rio de Janeiro) | Pinto da Silva, Tamires Pereira (Pontifical Catholic University of Rio de Janeiro) | Barreto, Abelardo Borges (Pontifical Catholic University of Rio de Janeiro) | Pesco, Sinésio (Pontifical Catholic University of Rio de Janeiro)
An object-based algorithm that models turbidite channels using training images, called skeleton-based simulation or SKESIM, is proposed in this study. These images are interpreted as a graph and used to extract the statistical distribution of parameters selected from the graph. From this information, a 3D model of turbidite channel systems was built. These channels were generated within the turbidite lobe, creating a simulated depositional system. After the geometry of the channels were simulated by SKESIM, the petrophysical properties were mapped by Gaussian-like distributions. Numerical simulations were used to fit the simulated permeability field to a reference case through an objective function. A commercial finite difference simulator was used to compare the reference data to the simulated data, and comparable results were obtained.
The purpose of this study was to develop a physical understanding of the bit damage that occurs in the Brushy Canyon and Avalon formations in the southern Delaware Basin and to develop practices to mitigate it. The operator had already implemented a programmatic initiative to move the organization toward physics-based, limiter-redesign workflows in order to achieve performance gains in a safe and efficient operation. A significant performance limiter was trips for damaged bits.
Two dominant causes of bit damage were observed. One was tangential overload of the outside cutters, which tends to occur if hard streaks are exited with high WOB and depth of cut (DOC). The second is continuous wear of the outside cutters that occurs if lower WOB is used to avoid the tangential overload. There was no operating window in which any given WOB did not enable one or the other form of damage in 12-1/4″ holes.
An explanation of how the overload may occur is presented along with the results of changes in field practices that were consistent with the concept. The progress that was made was partly due to physics-based training of operations personnel which enabled them to interpret observed behaviors and manage dysfunction more intensely. Some elements of the physics-based workflow and training are also discussed at length because they are integral to the improvements achieved in performance (
Bits from two wells drilled were pulled green after drilling from the surface casing through the Brushy Canyon. While this is encouraging the results from rig to rig was inconsistent. Bit design needs were identified that should enable higher success, and some of these features are now found in the current market. They were not available at the time of this initiative in 2018.
The nature of the interfacial severity damage varies from the southern to northern end of the Delaware basin, with laminar calcite streaks dominating in the south (the operator's acreage) and nodular chert inclusions occurring in some areas of the north. Both create high loading of a small number of cutter studs and the real time and engineering design practices that limit the interfacial severity damage discussed in this paper may be useful across the basin.
Panchal, Yashesh (Advantek Waste Management Services LLC) | Sameh, Omar (Advantek Waste Management Services LLC) | Mounir, Nihal (Advantek Waste Management Services LLC) | Shams, Mahmoud (Advantek Waste Management Services LLC) | Mohamed, Ibrahim (Advantek Waste Management Services LLC) | Abou-Sayed, Omar (Advantek Waste Management Services LLC) | Abou-Sayed, Ahmed (Advantek Waste Management Services LLC)
The injection of oil and gas wastes produced during the exploration and production phases have been proven to be an effective technique toward achieving zero discharge. However, several challenges are associated with the injection of slurry into an underground formation. The most common challenge during waste slurry injection (WSI) is the continuous loss of well injectivity due to poor engineering design of the injection parameters for most of the current existing WSI wells.
For the WSI operation, near wellbore formation damage (including the fracture damage) will be formed by the injected solids. The real time injection monitoring of the ongoing operations is important to correct any operational mistake and adjust the injection parameters in order to ensure the well longevity.
The paper discusses the importance of injection monitoring and steps necessary to maintain the injectivity and perform a healthy WSI operation. Three different case studies are presented to highlight the operational mistakes that caused a significant formation damage development in injectors in Eagle Ford, Haynesville, and Permian Basin shale plays. Certain guidelines depending on the monitoring results are provided in modifying the slurry rheology, pressure, injection strategy etc. that are helpful in maintaining the injectivity. The presented case studies show that the wells with good monitoring program maintained its injectivity during the course of its operation compared to the other wells that lost its injectivity sooner.
The results from different case studies are used to prepare a set of guidelines that can be used to maintain the well injectivity and extend the well life. This paper discusses the techniques that will help in eliminating and avoiding the problems leading to formation damage and well plugging during the WSI operation.
Semi-automation of hydraulic fracturing treatment designs often necessitates the application of simplified predictive models. Such models can only incorporate a limited subset of the relevant rock mechanical properties and an approximate representation of the stress state. This paper demonstrates the fundamental influence of three-dimensional stress states on the propagation of hydraulic fractures in coal seam gas (CSG) wells, and contrasts these results with those from two-dimensional simulations conducted in a one-dimensional stress state.
A three-dimensional, finite element-discrete element (FEM-DEM) model of a single well stage was developed as the basis for this study. This synthetic well was informed by case studies from the Surat Basin, Queensland, featuring varying complexity of key geomechnical factors. These include the existence of ∼30 coal seams within a gross rock column of more than 300 m, stress states that vary both laterally and vertically, ductile rock properties, and varying natural fracture densities and orientations. The developed model captures the full tensor description of stress, poroelastic-plastic modelling of the rock and coal, fully coupled fluid flow, and explicit modelling of fracturing.
The stress state was parametrically defined so that normal, strike-slip and reverse faulting conditions could be imposed and the magnitude of stresses varied to capture the appropriate range of varying conditions. A single perforation cluster was then used to induce a hydraulic fracture in an isotropic medium. Hydraulic fracture propagation (and propagation complexity) is influenced significantly by differential stresses, stress orientations and relative stress magnitudes. None of these are captured in two-dimensional simulations using a one-dimensional stress characterisation which is commonly derived from one-dimensional wellbore stress models.
The findings of this work clearly demonstrate the ability of fractures to turn and grow preferentially when they are not constrained to a two-dimensional plane. It also shows how the initiation of fractures (i.e. orientation to stress) impacts the propagation complexity of hydraulic fractures from the direction of maximum principal stress. In general, this paper highlights the benefit of incorporating the three-dimensionality of key geomechnical parameters when designing hydraulic fracturing stimulation treatments. Future work will incorporate greater reservoir detail (e.g. pressure-dependence, heterogeneity of stress and material properties) to further investigate fracture containment and reorientation.
The combination of extended-length horizontal drilling and high volume hydraulic fracturing has led to previously unimaginable production increases, yet the recovery potential of unconventional oil and gas resources remains largely unrealized. Recovery factors for unconventional oil and gas wells are typically reported at < 20% in gas shale reservoirs and < 10% in the oil plays.
Neutrally buoyant ultra-lightweight proppants have been demonstrated to effectively provide production from fracture area that is otherwise unpropped and thus, non-contributive with conventional sand/slickwater hydraulic fracturing processes. Production simulations illustrate that treatment designs incorporating neutrally buoyant ULW proppant treatment designs tailored for contemporary unconventional well stimulations deliver cumulative production increases of 30% to over 50% compared to the typical large volume sand/slickwater treatments. Unfortunately, production simulation results may not sufficiently lessen risk uncertainties for operators planning high-cost multi-stage horizontal stimulations. Therefore, several field trial projects using the neutrally buoyant ULW proppant in extended-length horizontal unconventional wells are currently in progress to validate the production simulations.
Since the initial 4-stage fracturing stimulation incorporating neutrally buoyant ultra-lightweight proppant in 2007, deployment has occurred in fracture stimulating hundreds of oil and gas wells spanning multiple basins and reservoirs. Most of the wells are vertical or relatively short lateral wells common to asset development practices predating the unconventional shale completions mania, but many were targeted at the same unconventional reservoirs as the current multi-stage horizontal completions. Several published case histories have documented the production enhancement benefits afforded by the legacy ULW proppant wells, but questions remained as to how those lessons might be correlated to provide engineers confidence in the current production simulations.
Well completion and production information was mined from the various accessible databases for the neutrally buoyant ULW proppant wells. The scope of the legacy data compiled for analysis was limited to the reservoirs common to the current field trials and production simulations, ie. unconventional oil and gas shale reservoirs. Production performance contributions of neutrally buoyant ULW proppant in past applications were compared with the production uplift observed in applications and/or simulated application of neutrally buoyant ultra-lightweight proppant fracturing treatments in current multi-stage horizontal reservoirs.
The lessons learned from this investigation provide the practicing engineer the means to confidently assess production simulation data for multi-stage horizontal unconventional completions incorporating neutrally buoyant ulw proppant in the treatment designs.
ABSTRACT: Ground control has been and continues to be a major problem facing underground mines around the world. Unplanned fall of ground (FoG) can lead to ore loss, accidents, fatalities and production delay. Hence, FoG is of critical importance to the design of underground mine excavations. Ground conditions, geological discontinuities, excavation geometry, support design measures and mining methods are fundamental factors influencing FoGs. Despite the advances in underground excavation design, there is still a need for developing tools capable of characterizing ground stability which is essential in estimating, controlling, monitoring damage and in the design of ground control procedures. Hence, this study focuses on FoG characterization and a FoG database has been compiled for this purpose. In order to quantify the rock mass behavior around underground excavations and fully characterize the FoG events, empirical methods and numerical methods were used. The Bamangwato Concessions Limited (BCL), an underground mine located in Selibe-Phikwe, Botswana, was used as a case study where FoG events that occurred in various stopes and other excavations were recorded. Overall, two aspects of the FoG characterization were investigated. Firstly, a FoG chart was proposed based on the Mathew's stability graph method with the purpose of predicting the ground class associated with FoG hazard. The stability of excavations was defined on the basis of the potential severity of FoG hazard as minor, moderate and major. Next, numerical modelling was implemented to analyze the modes of rock failure around the underground openings which had led to FoG. Rocscience Software Package was used to simulate the stress-induced and structure-induced failure modes or a combination of both that had been observed in the field. In general, the results were in agreement with the field data. It is concluded that this study has enhanced the understanding of ground conditions and FoG characteristics; and therefore could be used as a basis to provide recommendation for ground control improvements in BCL mines.
Williams, C. (Geotechnical Center of Excellence / University of Arizona) | Ross, B. (Geotechnical Center of Excellence / University of Arizona) | Zebker, M. (3vGeomatics Inc.) | Gaida, M. (Bingham Canyon Mine / Rio Tinto Kennecott Copper) | Morkeh, J. (Bingham Canyon Mine / Rio Tinto Kennecott Copper) | Robotham, M. E. (Rio Tinto Copper & Diamonds)
In April 2013, Rio Tinto Kennecott Copper's (RTKC) Bingham Canyon Mine experienced what is arguably the world's largest ever in-pit slope failure. The failure initiated on the East Wall, along a major, continuous, low-strength bedding fault, named the Manefay bed, and comprised approximately 145 million tonnes of rock and waste dump material. East wall slope deformations were detected some months prior to the catastrophic slope collapse by RTKC's ground based slope monitoring systems. Use of existing terrestrial radar and prism monitoring systems provided excellent data to manage the slope failure. The failure resulted in no injuries/loss of life, although the failure runout distance was larger than expected, resulting in the loss of mining equipment and significant production interruption.
Post failure investigations identified a RTKC sponsored, university research project which detected a zone of sporadic ground deformation at the crest of the Manefay failure using satellite based Interferometric Synthetic Aperture Radar (InSAR) data. When the outcomes of this research study were received in 2010, RTKC responded appropriately by conducting detailed field inspections and installing prisms in the area of concern.
Analytical methods for processing InSAR data have improved significantly since the time leading up to the Manefay failure. These updated methods have been used in this study of the available, historic InSAR data with results indicating that significant ground movements were occurring over a number of years prior to failure. Detailed knowledge of these movements could potentially have led to a different interpretation of failure mechanisms and magnitude and in hindsight, different slope management and mine development plans in the years preceding slope failure.
From a business and operations perspective, the ability to identify “weak signals” prior to catastrophic slope deformations is essential to appropriate management of such events. The use of InSAR, as discussed in this paper, provides an increased capability for further improved slope management at RTKC, and at other mining operations.
ABSTRACT: The mechanical properties of rock, such as unconfined compressive strength, are important to many engineering problems such as slope stability analysis, underground excavation, and drilling mechanics. Many previous studies have proposed relationships that can be used to estimate rock strength properties based on petrographic indices that are easier to measure. In this study, a comprehensive literature review was performed to build a database containing petrographic and mechanical properties for sedimentary rock types. A subset of this database containing only sandstone rock units was used for statistical analyses to develop predictive models. Linear and nonlinear bivariate models were constructed to relate each petrographic and physico-mechanical index variable to each mechanical property. Additionally, multiple regression models were developed using a subset of the petrographic and predictor variables. Contrary to prior studies using smaller data sets, very few correlations were identified, and those that were (for example dry density and mean grain size as predictors of UCS) tended to be for cases where limited data were available for the variables in question. A separate literature review was then performed to find previously-studied relationships that predict the strength properties of sandstones based on petrographic properties. 59 equations for sandstones were found and were tested against the broader sandstones database compiled in this study. It was found that many of these equations were developed for only one type of sandstone and tend to generalize poorly to the broader database.
Knowledge of a rock unit's geomechanical properties, such as unconfined compressive strength (UCS) and Brazilian tensile strength (BTS), can be valuable for many rock engineering applications. However, directly measuring a rock unit's geomechanical properties can be costly and time-consuming. As such, it is desirable to many geological and construction engineers to estimate geomechanical properties based on petrographic and physico-mechanical indices that are more easily measured. To identify these relationships between petrographic and geomechanical properties, several studies have developed empirical prediction equations for specific rock types using various statistical tools.