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Collaborating Authors
Australia
Poor rock conditions in a coal longwall panel can result in roof collapse when a problematic zone is mined, significantly interrupting mine production. The ability to image rock conditions โ stress and degree of fracturing โ ahead of the face gives the miners the ability to respond proactively to such problems. This method uses the energy from mining machinery, in this case a coal shearer, to produce an image of the rock velocity ahead of the mining face without interrupting mining. Data from an experiment illustrates the concept. Geophones installed in gate-road roofs record the noise generated by the shearer after it has traversed the panel ahead of the mining face. A generalized crosscorrelation of the signals from pairs of sensors determines relative arrival times from the continuous seismic noise produced by the shearer. These relative times can then be inverted for a velocity structure. The crosscorrelations, performed in the frequency domain, are weighted by a confidence value derived from the spectral coherence between the traces. This produces stable crosscorrelation lags in the presence of noise. The errors in the time-domain data are propagated through to the relative traveltimes and then to the final tomographic velocity image, yielding an estimate of the uncertainty in velocity at each point. This velocity image can then be used to infer information about the stress and fracture state of the rock, providing advance warning of potentially hazardous zones.
- Geophysics > Seismic Surveying > Surface Seismic Acquisition (0.74)
- Geophysics > Seismic Surveying > Seismic Processing (0.48)
- Materials > Metals & Mining (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Information Technology > Data Science (0.68)
- Information Technology > Artificial Intelligence > Representation & Reasoning > Uncertainty > Bayesian Inference (0.46)
- Information Technology > Artificial Intelligence > Machine Learning > Learning Graphical Models > Directed Networks > Bayesian Learning (0.46)
Reservoir rocks are often saturated by two or more fluid phases forming complex patterns on all length scales. The objective of this work is to quantify the geometry of fluid phase distribution in partially saturated porous rocks using statistical methods and to model the associated acoustic signatures. Based on X-ray tomographic images at submillimeter resolution obtained during a gas-injection experiment, the spatial distribution of the gas phase in initially water-saturated limestone samples are constructed. Maps of the continuous variation of the percentage of gas saturation are computed and associated binary maps obtained through a global thresholding technique. The autocorrelation function is derived via the two-point probability function computed from the binary gas-distribution maps using Monte Carlo simulations.The autocorrelation function can be approximated well by a single Debye correlation function or a superposition of two such functions. The characteristic length scales and show sensitivity (and hence significance) with respect to the percentage of gas saturation. An almost linear decrease of the Debye correlation length occurs with increasing gas saturation. It is concluded that correlation function and correlation length provide useful statistical information to quantify fluid-saturation patterns and changes in these patterns at the mesoscale. These spatial statistical measures are linked to a model that predicts compressional wave attenuation and dispersion from local, wave-induced fluid flow in randomly heterogeneous poroelastic solids. In particular, for a limestone sample, with flow permeability of 5 darcies and an average gas saturation of , significant -wave attenuation is predicted at ultrasonic frequencies.
- North America > United States (0.46)
- Oceania > Australia (0.28)
- Geology > Geological Subdiscipline > Geomechanics (0.46)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Limestone (0.45)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Gas-injection methods (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (0.89)
Summary This paper presents the results of a data-driven, field-modeling (DDFM) evaluation applied to a high-temperature reservoir in Australia for the purpose of determining the significance of chemistry, reservoir, well, and hydraulic-fracture characteristics on well production. The DDFM approach has identified key production drivers for a gas-well field in Australia. This information has been useful in explaining hydraulic-fracture well production and providing guidelines for future fracture stimulation success. A DDFM process is used to develop a model for 32 wells completed in a complex, 250 to 350ยฐF gas reservoir in Australia. This type modeling technique uses data from the field, including chemical formulation, geology, reservoir, well, completion, hydraulic-fracture stimulation, and production results. The data is integrated into a common format and resolution, and then a visual and statistical evaluation is performed. Relevant correlations and useful trends are noted. Next, an effort is made to develop a predictive model that can be used to provide an overall explanation as to what parameters drive production in the well field. Or, in effect, derive a high-level understanding about the effect of the fracturing process on the reservoir. This is accomplished by the use of data modeling/optimization technologies, including artificial neural network (ANN) and genetic algorithms. The resulting ANN model can then be used to evaluate the production associated with various hydraulic-fracturing scenarios and/or characteristics. Validation of conclusions and/or resolution of difficult interpretation issues are done by detailed evaluation and modeling of key wells. Hydraulic-fracture stimulation scenario evaluations performed by the ANN model have yielded some expected as well as unexpected results. As expected, reservoir characteristics, such as pay thickness, porosity, and water saturation have a dominant effect on well production. What was unexpected is the significance of well operations and stimulation fluid chemistry on well production. The practice of killing the well after stimulation and using inappropriate perforation techniques can reduce gas production by as much as one-half, while the use of a high-temperature gel breaker in combination with a reduction in base-gel polymer load can provide a 67% increase in production. Introduction This paper analyzes reservoir, well, and completion information from the Toolachee and Daralingie formations in the Moomba and Big Lake fields. The work focuses primarily on the performance of fracture-stimulated wells. The specific objectives were as follows:Attempt to predict post-fracture production from available preproduction data. Identify key parameters that influence fracture effectiveness and production performance. Determine which completion/stimulation methods and designs have been successful in the past, and use the information to improve future designs. Use the three previously listed understandings to improve fracture candidate selection. In turn, a more general objective is to perform a pilot trial to determine the applicability and benefits of applying ANN analysis as a tool for understanding and improving well performance as part of a 1999 integrated reservoir study. For well-performance comparison purposes, a 12-month, normalized, cumulative production volume (NCPV) for each well is determined. Because wells from all stages of the field life are considered, this normalization removes the effect of declining reservoir pressures or changes in surface pressures caused by installation of compression, etc. The 12-month NCPV is determined for a "datum" reservoir pressure of 3,600 psi and a flowing tubing head pressure of 500 psi by multiplying the first 12-month actual cumulative gas production volume by (3,600 to 500)/(reservoir pressure - ftp).
- Oceania > Australia (0.95)
- North America > United States > Texas (0.75)
- Asia > Middle East > Israel > Mediterranean Sea (0.24)
- Oceania > Australia > South Australia > Cooper Eromanga Basin > Big Lake Field (0.99)
- Oceania > Australia > South Australia > Cooper Eromanga Basin > Moomba Field > Toolachee Formation (0.96)
- Oceania > Australia > South Australia > Cooper Eromanga Basin > Moomba Field > Daralingie Formation (0.96)
- (4 more...)
Increasing Reservoir Contact by Combining Mechanical Diversion and Unique Stimulation Chemistry
Veillette, Christian Patrick (Enduring Resources) | Cuzella, Jerome (Enduring Resources) | Mueller, Fred A. (Schlumberger) | Loayza, Michael Paul (Schlumberger) | Malaver, Rafael (Schlumberger) | Abaza, Bayan (Schlumberger) | Gurmen, M. Nihat (Schlumberger)
Abstract The Edwards Limestone in South Texas often requires stimulation to be commercially productive. The relatively low permeability, high Young's Modulus, presence of natural fractures, minimal stress barriers to control height growth, and formation temperatures up to 375ยฐF provide a challenging environment for a successful stimulation. Conventional stimulation approaches using acid fracturing and proppant fracturing techniques often have resulted in less than optimal effective etched or propped fracture half lengths, respectively. Horizontal openhole completions have increased the potential reservoir contact to the wellbore, but are not effective without stimulation. Achieving the diversion along the horizontal wellbore that is required to effectively treat the entire interval proved difficult using conventional diversion techniques with particulate and chemical diversion. Furthermore, the difficulty in achieving sufficient fracture width limits the proppant concentration that can be pumped into the formation. Acid fracturing was a desirable stimulation technique, but because of the high reservoir temperature and associated high acid spending rate, it was difficult to achieve a long effective etched half length with acid fracturing. A unique approach was developed by combining a novel diversion technique with a new stimulation treatment. The diversion technique enables mechanical isolation of the openhole completion during the stimulation treatments. The mechanical diversion system also facilitates efficient pumping of multiple stimulation treatments, resulting in increased reservoir contact to the wellbore. The new stimulation treatment uses a unique lightweight (1.25 SG) proppant-like material that is pumped into the well as an inert substance. The product hydrolyzes only after the solid particles are in the reservoir for an amount of time at temperature. This enables the fracture etching process to occur during shut-in and flowback of the well thus solving the problem of creating long effective etched fracture half lengths with acid. The combination of these two techniques has enabled a much larger stimulated reservoir contact to the wellbore in the Edwards Limestone in South Texas, which leads to improved production. Introduction The Edwards Limestone reef trend is a natural gas play that runs from South to East Texas with a northeasterly trend. The productive section in the Bee, Karnes, and Dewitt tri-county area is part of the greater Stuart City Reef Trend (Fig. 1). A detailed geological description is discussed in the next section. Geology The Edwards formation consists of fossiliferous limestone that was deposited in a complex of related environments that include biogenic reefs, banks, tidal bars, islands, and channel fills developed along the basinward edge of a carbonate shelf. The shelf almost completely encircled the ancestral Gulf of Mexico during the Early to Middle Cretaceous period. The reefal buildups, which developed along a high-energy shelf margin, were able to maintain their growth positions against a rapidly rising sea level that resulted in vertical accretion. A depositional break in slope developed basinward of the reef systems as insufficient sediment accumulated beyond the reefs resulting in a distinct shelf edge. The Edwards Limestone conformably overlies the Glen Rose Limestone, which together makes up the Stuart City, and is approximately 2,000 ft thick. Separated by the Pearsall Shale, which is approximately 460 ft thick, is the underlying Sligo Limestone. The Edwards Limestone is overlain by the Georgetown Limestone in varying thicknesses up to 95 ft; it is in turn overlain by the Eagle Ford Shale as shown in the stratigraphic column in Fig. 2 (Wooten and Dunaway, 1977).
- North America > United States > Texas (1.00)
- Oceania > Australia > Victoria > Bass Strait (0.25)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Limestone (1.00)
- Geology > Geological Subdiscipline (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.44)
- North America > United States > Texas > West Gulf Coast Tertiary Basin > Pawnee Field (0.99)
- North America > United States > Texas > West Gulf Coast Tertiary Basin > Edwards Formation (0.99)
- North America > United States > Texas > West Gulf Coast Tertiary Basin > Eagle Ford Shale Formation (0.99)
- (7 more...)
Abstract In the design of hydraulic fractures, it is necessary to make simplifying assumptions. Fifty years ago, our industry was mathematically obliged to describe fractures as simple, planar structures when attempting to predict fracture geometry and optimize treatments. Although computing tools have improved, as an industry we remain incapable of fully describing the complexity of the fracture, reservoir, and fluid flow regimes. Generally, we make some or all of the following assumptions:โSimple, planar, bi-wing fractures โCompletely vertical fractures with perfect connection to the wellbore โFlow capacity that is reasonably described by published conductivity data โPredictable fracture width providing dependable hydraulic continuity (lateral and vertical continuity) To forecast production from these fractures, we frequently make the additional assumptions:โReservoir is laterally homogeneous โModest/no barriers to vertical flow in formation (simplified description of layering compared to reality) However, we must recognize that all of these assumptions are imperfect. This paper will investigate the evidence suggesting that fractures are often subject to:โComplicated flow regimes โComplicated geometry โIrregular frac faces โImperfect proppant distribution โImperfect hydraulic continuity โImperfect wellbore-to-fracture connection โResidual gel damage, possibly including complete plugging or fracture occlusion Additionally, reservoirs are known to contain flow barriers that amplify the need for fractures to provide hydraulic continuity in both vertical and lateral extent. The paper appendix tabulates the results from more than 200 published field studies in which fracture design was altered to improve production. Frequently the field results cannot be explained with our simplistic assumptions. This paper will list the design changes successfully implemented to accommodate real-world complexities that are not described in simplistic models or conventional rules of thumb. Field examples from a variety of reservoir and completion types [tight gas, modest perm oil, coalbed methane, low rate shallow gas, annular gravel packs] will be provided to demonstrate where the field results differ from expectations, and what adjustments are necessary to history-match the results.
- South America > Brazil (1.00)
- Oceania > Australia (1.00)
- North America > United States > Wyoming (1.00)
- (24 more...)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.97)
- Geology > Structural Geology (0.68)
This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 112125, "Multi Lateral Horizontal Well Application for Improving the Oil Recovery of a Mature Field, Intisar N. Field, Concession 103 - Libya," by M.M. Gharsalla and M.B. Elghmari, Zueitina Oil Company, originally prepared for the 2008 SPE North Africa Technical Conference and Ex hib ition, Marrakech, Morocco, 12-14 March. The paper has not been peer reviewed. The full-length paper examines the performance of a multilateral completion in a mature thin carbonate reservoir. The initial field development with two vertical wells resulted in a poor recovery of only 9% of the original oil in place. A reservoir-simulation study in 2003 indicated that drilling vertical wells in a very thin reservoir of poor quality was not cost-effective and recommended drilling horizontal wells. The stabilized oil-production rate of the multilateral horizontal well was approximately three times higher than that of the vertical well. Introduction Intisar N field is in Concession 103 in Libya approximately 360 km south of Benghazi in the prolific Sirte basin. The field was discovered in 1968 by drilling Well N1 to a total depth of 10,318 ft in the Lower Sabil. The Intisar N field comprises two separate carbonate reservoirs, the Upper Sabil (Zelten) at a depth of 9,230 ft and Lower Sabil (Heira) at 9,820 ft, approximately 600 ft apart. Fig. 1 shows a map of formation tops of the Upper Sabil and Lower Sabil formations. Both reservoir structures are composed of two anticlinal saddles believed to be separated by a fault. The field is relatively small in size, with initial oil in place of 19.0 million STB of which 14.4 million STB is contained in the Zelten (Upper Sabil) reservoir and 4.6 million STB in the Heira (Lower Sabil) reservoir. Stratigraphy and Trapping Mechanism The general stratigraphy and structure in the Concession 103 area has been controlled by the shelf edge in Upper Paleocene times between the Marsa Brega Trough and the Gialo/Amal high. Reefal bioherms developed on this shelf edge through the Upper Paleocene, after which there was a transgression or subsidence in the very late Paleocene resulting in the deposition of the Kheir marls and shale. During the Eocene, there was predominantly shelf carbonate deposition, with the grain size determined by provenance and water depth. Locally, the sedimentation has been influenced by drape over the reef, resulting in locally shallow water depths in the immediate area of the reef, resulting in rather gentle homoclines providing up to 50 to 70 ft of closures. The oil accumulations at Concession 103N in the Zelten and Heira reservoirs are trapped by the homoclines. Petrophysical Properties The reservoir quality varies laterally significantly in both the Upper and Lower Sabil; the quality improves toward the crest and deteriorates toward the flanks. Most parts of the Upper Sabil formation have fair porosity, and good solution porosity is locally present. The oil systems in the Upper and Lower Sabil reservoirs are light and highly undersaturated.
- Oceania > Australia > Victoria > Bass Strait (0.45)
- Africa > Middle East > Libya > Banghazi District > Benghazi (0.25)
- North America > United States > Oklahoma > Anadarko Basin > Light Field (0.99)
- Africa > Middle East > Libya > Sirte District > Sirte Basin > Rakb Group Formation > Sirte Shale Formation (0.94)
President's column As I move further into my year as president, I have been refining my key message as follows: inherent in, and fundamental to, SPE's mission is the notion of and adherence to a number of values and principles. These include that SPE is a member organization, as opposed to a corporate organization, and individuals are members of SPE. These individuals belong to SPE to develop and broaden their skills as oil and gas professionals in a worldwide industry as well as to network with other individuals (technical specialists). Inevitably, each individual member brings to SPE a measure of his/her company self-interest and culture, and this adds to the diversity of SPE's international membership. Corporate culture benefits SPE directly: companies sponsor SPE initiatives and exhibit at SPE events, and they allow their employees time and funds to participate in SPE committees and activities. Thus, SPE benefits not only from an altruistic desire on the part of individuals to further technology dissemination, but also from companies wishing to be seen to engage in the Society's activities and to support its mission. Early October saw me in New Zealand and Australia. I was delighted to find that these SPE values and principles are very well understood here. Volunteerism is perceived by both individuals and companies to offer great value, and all sections have very active board members. I began this trip with a visit to New Plymouth in New Zealand. This section is small, with 82 members, including 16 young professionals. Typically, between 15 and 30 members regularly attend lunch meetings, which are organized jointly with the New Zealand Institute of Professional Engineers. No university in New Zealand offers a petroleum engineering course, so there are no student members. However, the section sponsors scholarship programs for engineering students at three New Zealand universities. I then flew to Australia, where I visited the Queensland Section in Brisbane, the South Australian Section in Adelaide, and the Western Australian Section in Perth. Membership in all six Australian sections, including New South Wales/Australian Capital Territory, Victoria and Tasmania, and Northern Territory, totals some 1,500. Australia is Huge (with a capital H indeed) and each section has a different focus. For example, 75% of the Queensland Section members work in the booming coalbed methane (CBM) business. There are plans to build four liquefaction plants to start CBM exports to Japan and China. However, the business is dominated by small and medium-sized independent companies, and they are currently finding it difficult to raise funds for further developments due to the credit crunch. Another interesting development in that region is underground coal gasification (UCG). Linc Energy, which is seeking to utilize UCG and gas-to-liquid technologies as a means of converting coal deposits into liquid fuel, is at the forefront of Australian UCG development. My next stop was Adelaide, home to the South Australian Section, founded in 1982 and thus the oldest of the Australian sections. The other five Australian sections were set up between 1983 and 1990. In addition to its monthly meetings, the South Australian Section organizes such activities as Education Day, where 70 high school students are exposed to our industry, and an annual math competition with the Math Association.
- Oceania > Australia > South Australia (0.66)
- Oceania > Australia > Queensland (0.45)
- Energy > Oil & Gas > Upstream (1.00)
- Education > Educational Setting > K-12 Education > Secondary School (0.53)
- Oceania > Australia > Western Australia > North West Shelf > Carnarvon Basin > Dampier Basin > WA-253-P Permit > Block WA-253-P > Wheatstone Field > Mungaroo Formation (0.93)
- Oceania > Australia > Western Australia > North West Shelf > Carnarvon Basin > Dampier Basin > WA-253-P Permit > Block WA-17-R > Wheatstone Field > Mungaroo Formation (0.93)
- Oceania > Australia > Western Australia > North West Shelf > Carnarvon Basin > Dampier Basin > WA-253-P Permit > Block WA-16-R > Wheatstone Field > Mungaroo Formation (0.93)
- (6 more...)
Direct laboratory observation of patchy saturation and its effects on ultrasonic velocities
Lebedev, Maxim (Karlsruhe University) | Toms-Stewart, Julianna (Karlsruhe University) | Clennell, Ben (Karlsruhe University) | Pervukhina, Marina (Karlsruhe University) | Shulakova, Valeriya (Karlsruhe University) | Paterson, Lincoln (Karlsruhe University) | Mรผller, Tobias M. (Karlsruhe University) | Gurevich, Boris (Karlsruhe University) | Wenzlau, Fabian (Karlsruhe University)
Maximizing the recovery of known hydrocarbon reserves is one of the biggest challenges facing the petroleum industry today. Optimal production strategies require accurate monitoring of production-induced changes of reservoir saturation and pressure over the life of the field. Time-lapse seismic technology is increasingly used to map these changes in space and time. However, until now, interpretation of time-lapse seismic data has been mostly qualitative. In order to allow accurate estimation of the saturation, it is necessary to know the quantitative relationship between fluid saturation and seismic characteristics (elastic moduli, velocity dispersion, and attenuation). The problem of calculating acoustic properties of rocks saturated with a mixture of two fluids has attracted considerable interest (Gist, 1994; Mavko and Nolen-Hoeksema, 1994; Knight et al., 1998. For a comprehensive review of theoretical and experimental studies of the patchy saturation problem see Toms et al., 2006).
- Research Report > New Finding (0.34)
- Overview (0.34)
- Geophysics > Time-Lapse Surveying > Time-Lapse Seismic Surveying (1.00)
- Geophysics > Seismic Surveying (1.00)
The Kristineberg mining area in the western part of the Paleoproterozoic Skellefte Ore District, northern Sweden, is well known for its base-metal and recent gold discoveries. A pilot 3D geologic model has been constructed on a crustal scale, covering an area of to depths of . Constrained 3D inverse and forward gravity modeling have been performed to confirm and refine previous modeling along seismic profiles using mainly 2.5D techniques. The 3D inverse gravity modeling was geared to generating isodensity surfaces that enclose regions within the model of anomalous density contrast. The 3D forward gravity modeling was conducted to include faulting and folding systems that are difficult to include in the inversion. The 3D geologic model supports many previous interpretations but also reveals new features of the regional geology that are important for future targeting of base-metal and gold deposits. The margins of a thick granite in the south dip steeply inward, suggesting the possibility of room to accommodate another large base-metal deposit if the granitic rocks are juxtaposed with volcanic rocks at depth. Gravity modeling also suggests the observed Bouguer gravity high within the western metasediments can be explained by a large mafic intrusion that has dioritic to tonalitic composition and no significant magnetic signature. Because mafic-ultramafic intrusions within metasediments can indicate gold, this interpretation suggests the western metasediments have a high gold potential.
- Europe > Sweden (0.86)
- Oceania > Australia (0.67)
- North America > Canada (0.67)
- Geology > Structural Geology > Tectonics (1.00)
- Geology > Rock Type > Igneous Rock (1.00)
- Geology > Geological Subdiscipline (1.00)
- Geology > Mineral > Native Element Mineral > Gold (0.86)
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Gravity Surveying > Gravity Modeling > Gravity Inversion (0.69)
- Materials > Metals & Mining (1.00)
- Energy > Oil & Gas > Upstream (1.00)
Abstract Esso Australia Pty Ltd has recently completed a control and protective system upgrade at its LPG fractionation plant at Long Island Point in Victoria. The upgrade included a new control building, new process control system, new instrument equipment room, field instruments and upgrade of the plant's relay based shutdown system. This paper describes how the project incorporated contemporary human factor principles in its design of the new control building and the control system. The control room design considered its purpose and role of the operator. The control system graphic displays were developed to provide operators with an effective interface by presenting information in a consistent manner and prioritised through use of colour, shape and line dynamics. Established Alarm Management principles were used to capture, validate and prioritise alarms. In the event of an abnormal situation, feedback and guidance is made available to the operator for appropriate action. Innovative features were implemented in the control system to reduce human error and enhance reliability of operation. Intelligent software reset facility has improved efficiency of restarting the plant after a shutdown. A popup display table informs the operator of any interlock conditions affecting plant operation. Access to Asset Management System of intelligent field devices is made available from the operating face plates. Commonly known Windows style formatting for all indications and operator actions facilitated steep learning for a workforce unfamiliar with screen based operating systems. There was an extensive and ongoing involvement of plant personnel in all phases of the project. All graphic displays were planned, reviewed and tested with the involvement of operators. The outcome of considering human factors in design has been end user acceptance with benefits of enhanced safety and opportunity for improved productivity.
- Facilities Design, Construction and Operation > Measurement and Control > Process control and automation (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
- Health, Safety, Environment & Sustainability > Health > Ergonomics (0.92)
- Health, Safety, Environment & Sustainability > Safety > Human factors (engineering and behavioral aspects) (0.83)