Present day innovations in seismic acquisition tools and techniques have enabled the acquisition of detailed seismic datasets, which in many cases are extremely large (on the order of terabytes to petabytes). However, data analysis tools for extracting information on critical subsurface features such as fractures are still evolving. Traditional methods rely on time-consuming iterative workflows, which involve computing seismic attributes, de-noising and expert interpretation. Additionally, with the increasingly widespread acquisition of time-lapse seismic surveys (4D), there is a heightened demand for reliable automated workflows to assist feature interpretation from seismic data.
We present a novel data-driven tool for fast fracture identification in BIG post-stack seismic datasets, motivated by techniques developed for real-time face detection. The proposed algorithm computes spatiotemporal amplitude statistics using Haar-like bases, in order to characterize the seismic amplitude properties that correspond to fracture occurrence in a unit window or voxel. Under this approach, the amplitude data is decomposed into a collection of simple-to-calculate "mini-attributes", which carry information on the amplitude gradient and curvature characteristics at varying locations and scales. These features then serve as inputs to a cascade of boosted classification tree models, which select and combine the most discriminative features to develop a probabilistic binary classification model. This overall approach helps to eliminate the computationally-intensive and subjective use of ad-hoc seismic attributes in existing approaches.
We first demonstrate the viability of the proposed methodology for identifying discrete macro-fractures in a 2D synthetic seismic dataset. Next, we validate the approach using 3D post-stack seismic data from the Niobrara Shale interval within the Teapot Dome field. We show the applicability of the proposed framework for identifying sub-seismic fractures, by considering the amplitude profile adjacent to interpreted fullbore microimage (FMI) well log data. The upscaled spatial distribution of the predicted fractures shows agreement with existing geological studies and align with interpreted large-scale faults within the interval of interest.
This paper was prepared for presentation at the Unconventional Resources Technology Conference held in Houston, Texas, USA, 23-25 July 2018. The URTeC Technical Program Committee accepted this presentation on the basis of information contained in an abstract submitted by the author(s). The contents of this paper have not been reviewed by URTeC and URTeC does not warrant the accuracy, reliability, or timeliness of any information herein. All information is the responsibility of, and, is subject to corrections by the author(s). Any person or entity that relies on any information obtained from this paper does so at their own risk.
Haridy, Mohamed Galal (University of Aberdeen) | Sedighi, Farzaneh (Sciencore Ltd) | Ghahri, Panteha (University of Aberdeen, Oil and Gas Authority) | Ussenova, Kamshat (Schlumberger) | Zhiyenkulov, Murat (Schlumberger)
Naturally fractured reservoirs (NFR) possess one-third of the global hydrocarbons reserves. An accurate modelling of the fracture network is the key for a successful and economically efficient prediction of oil recovery. As the dual porosity/permeability models do not honor the connectivity and spatial variation of fracture properties, they are integrated with the discrete fracture network model (DFN). Choosing an appropriate technique for upscaling the permeability of the DFN model is vital for maximizing oil recovery from NFRs. In one hand, the numerical, flow-based, upscaling method is sophisticated in terms of accuracy, however, its CPU-intensive nature deems it inapplicable for full field studies. In the other, the analytical Oda method is computationally efficient, albeit it is only accurate for well-connected fractures. Consequently, these issues are addressed in the semi-analytical Oda corrected method which accounts for the connectivity of fractures. Nevertheless, owing to the fact that it has been recently developed, it has not been sufficiently studied to investigate its limitations and advantages.
This study aims to analyze the static and dynamic performance of the aforementioned upscaling methods. To achieve this, sensitivity analysis was performed on various fracture properties via a numerical simulator and realistic field data. For all comparisons, the flow-based method was used as a reference solution, due to its accuracy. Indeed, the analysis revealed that the new Oda corrected method can calculate the equivalent permeability tensor with adequate accuracy. However, it overestimates the permeability when fracture networks are below the percolation threshold and/or when fractures length is large. Hence, this method is recommended for networks with moderate to high intensity. Furthermore, it has been deduced that fracture length has a great impact on the connectivity of fractures, albeit its effect on permeability is limited by the intensity of fractures. Additionally, it has been found that the length of fractures has an immense impact on the anisotropy ratio and control the occurrence of water bypassing, which were not captured by the Oda method.
Ross, T. S. (New Mexico Institute of Mining & Technology) | Rahnema, H. (New Mexico Institute of Mining & Technology) | Nwachukwu, C. (New Mexico Institute of Mining & Technology) | Alebiosu, O. (ConocoPhillips Co) | Shabani, B. (Oklahoma State University)
Steam injection—a thermal-based enhanced oil recovery (EOR) process—is used to improve fluid mobility within a reservoir, and it is well known that it yields positive results in heavy-oil reservoirs. In theory, steam injection has the potential of being applied in light-oil reservoirs to enable vaporization of in-situ reservoir fluids, but field developments and scientific studies of this application are sparse. Conventional displacement methods like water-flooding and gas-flooding have been applied to some extent, however, oil extraction in such reservoirs relies on recovery mechanisms like capillary imbibition or gravity drainage to recover oil from the reservoir matrix. Furthermore, low-permeability reservoir rocks are associated with low gravity drainage and high residual oil saturation.
The objective of this study is to evaluate the potential of steam injection for light (47°API) oil extraction in naturally-fractured reservoirs. It is theorized that this method will serve as an effective tool for recovery of light hydrocarbons through naturally-fractured networks with the benefit of heat conduction through the rock matrix. This research investigates the application of light-oil steamflood (LOSF) in naturally- fractured reservoirs (NFR).
A simulation model comprised of a matrix block surrounded by fracture network was used to study oil recovery potential under steam injection. To simulate gravity drainage, steam was injected through a horizontal well completed in the upper section of the fracture network, while the production well was completed at the bottom of the fracture network. The simulation included two different porous media: (1) natural fractures and (2) matrix blocks. Each of these porous media was assumed to be homogeneous and characterized based on typical reservoir properties for carbonate formations. This study also analyzed the impact of different recovery mechanisms during steam injection for a light-oil sample in NFR, with reservoir sensitivity examined, based on varying amounts of vaporization, injection rate, permeability, matrix height and capillary pressure. Of these, vaporization was found to be the dominant factor in the application of LOSF in NFR, as described in detail within the results.
We develop a workflow for sequential correlation of multiple well logs following an optimal path that preserves maximum coherency between neighboring log traces. In order to find an optimal sequence along multiple correlation pairs, we formulate this problem as solving the traveling salesman problem (TSP). The ”distances” between wells are defined as geometric distances weighted by log coherences measured by local similarity attribute, thus formulating a non-Euclidean graph. We adopt genetic algorithm (GA) to find the solution with near optimization in an efficiently feasible computation. Numerical examples demonstrate that the proposed method can achieve effective and efficient correlation of multiple well logs.
Presentation Date: Tuesday, September 26, 2017
Start Time: 3:55 PM
Presentation Type: ORAL
Co-produced water resources in oil & gas fields raise technological interest under the condition of increased energy demand and carbon dioxide emission reduction. Primarily the development of medium and lowtemperature co-produced water resources are discussed in terms of energy production and further utilization in the downstream facilities of petroleum industry. Addition of the Organic Rankine cycle (ORC) as a compact binary power plant to the existing scheme allows harvesting a great portion of energy that is usually lost as waste heat. This additional system does not interrupt the main facility streams and operational parameters. The simple case with R134a refrigerant was numerically explored for the wide range of coproduced water flow rates and temperatures. The results show that with the increase of water production the power generation is increased up to 1 MW at 50,000 BWPD and 275 F water temperature. The economic evaluation shows that the Levelized cost of electricity falls lower than 1.5 cents/kW.
Cement deteriorates when exposed to acidic environment such as carbonic acid, sulfuric acid and hydrochloric acid. The rate of acid attack is influenced by pressure and temperature among other parameters. Real world scenarios involving practical exposure of well cement to these aggressive fluids include CO2-EOR, carbon capture and storage, CO2/H2S co-sequestration and matrix acidizing. The origin of cement degradation can be due to physical, chemical or mechanical processes or combination of these. Chemical degradation occurs when cement reacts with aggressive fluids to form minerals that are easily leachable or susceptible to further reaction. Cement exposed to brine saturated with Co2 undergoes combination of processes which includes hydration and chemical shrinkage, expansion and thermally induced pressurization, structural transformation of calcium silicates, decalcification, carbonation, bi-carbonation and mineral leaching. The degree of occurrence of these processes are controlled by temperature, CO2 gas composition, pressure, slurry composition and brine concentration. The objective of this study is to better understand the mechanisms governing the degradation process and quantify the rate of deterioration experimentally. This paper describes the mechanisms involved in the degradation of well cement in high pressure and high temperature (HPHT) carbonic acid environment.
To understand the cement degradation mechanisms, previously published experimental data (compressive strength, porosity, permeability and FTIR mineralogy) is augmented with aging fluid calcium content measurements and photographic images of bisected specimens to further interpret the results. Aging fluid samples were collected after degradation test and chemical analysis was conducted to quantify calcium content. During the test, brine saturated with a gas mixture of carbon dioxide and methane was used to generate aggressive environment around the cement specimens.
Results show improvement in mechanical and transport properties of cement specimens, although the specimens were physically and chemically degraded. Three mechanisms of degradation are identified as the driver of the degradation process. Structural transformation of calcium silicates at elevated temperature leads to slight retrogression in strength. Carbonation reaction improves mechanical strength but reduces porosity and permeability. Bicarbonation and leaching reactions increase porosity and permeability leading to the loss of mechanical strength. These mechanisms occur concurrently; the overriding process governs the rate of degradation. Within the experimental time scale adopted in this study, carbonation is the rate-controlling process because the overall integrity of the cement is improved. These results indicate that cement sheath is chemically degraded when exposed to carbonated brine under HPHT conditions.
Very limited studies have been conducted to evaluate cement performance under HPHT acidic environment. The analysis presented in this paper sheds light on how common oil well cements degrade under extreme borehole conditions.
Vajpayee, Mudit (Pandit Deendayal Petroleum University) | Martolia, Ramchandra Singh (Pandit Deendayal Petroleum University) | Chanchlani, Kuldeep (Pandit Deendayal Petroleum University) | Mehta, Mohit (Pandit Deendayal Petroleum University) | Chauhan, Arjun (Pandit Deendayal Petroleum University) | Sodani, Anurag (Pandit Deendayal Petroleum University)
Historically, the co-softhyphen;produced hot water has been an inconvenience and a disposal issue for oilfield operators. This paper focuses on brine or coproduced fluids (hot aqueous fluids produced during oil and gas production) as a potential source for electricity generation, which could be produced from the thermal energy available in the produced fluid. Oil and Gas (O&G) industry today is in possession of thousands of established wells with known temperatures and flows which can be used for producing emissions-free and cost-competitive electricity using binary cycle units.
Power generation from coproduced fluids using a binary-cycle power plant is underway at the Rocky Mountain Oilfield Testing Center in Wyoming and being considered in locations in Texas, Louisiana, Florida, and Arkansas. Although currently there is no electricity generated from coproduced fluids in India, various studies, suggest that the oil and gas fields in the Cambay Basin basin have a promising geothermal gradient of 35-40 °C/km, while (
In this paper, we studied and collated data of Jhalora Field in Mehsana asset of Cambay Basin for coproduction electricity generation and attempt to provide an estimate of the coproduced-water-electricity-generation potential of that field using two different approaches.
The most significant parameters to economic viability for such a project include reservoir temperature as well as total fluid production rate. The reservoir temperature of Jhalora Field is 90-100°C and with produced water flow rate of 5096m3/day, it is a suitable candidate for application of this technology.
Towler, Brian F. (School of Chemical Engineering, The University of Queensland) | Firouzi, Mahshid (School of Chemical Engineering, The University of Queensland) | Holl, Heinz-Gerd (Centre for Coal Seam Gas, The University of Queensland) | Gandhi, Randeep (QGC Pty. Ltd) | Thomas, Anthony (QGC Pty. Ltd)
Many field trials have been conducted to explore the effectiveness of using hydrated bentonite as a sealing material for plugging and abandoning (P&A) operations of oil and gas wells. Many of those trials are reviewed here, including trials in Texas, New Mexico, Oklahoma, Wyoming and Queensland, most of which have not been previously reported. All of these trials have been successful, even though a few wells have been eliminated from the programs because they were found to be unsuitable. In most jurisdictions regulation changes are necessary to allow bentonite to be used in order to plug wells. This has been done in California, Texas and Oklahoma. In Wyoming it is currently permitted as the bottom plug in coal-bed methane wells. In Queensland a field trial has been allowed under the experimental materials clause in the regulations.
Pennsylvania has a 150-year history of oil and gas production-the longest of any state- and this enduring activity has resulted in the drilling of more than 330,000 known wells. However, unknown wells may exist because innumerable wells were drilled during Pennsylvania's early years of intense oil and gas development when incomplete records were kept of well locations. The concern is that early wells are likely to be unsealed because there were no laws that required effective plugging when the wells were abandoned. Now, many unrecorded wells are thought to be in areas of emerging shale gas and shale oil development where open wellbores might provide a pathway for undesired upward migration of fluids and gas from hydraulically fractured reservoirs. Because of this concern, Pennsylvania regulators have asked operators to locate orphaned and abandoned wells within a 1000-ft- buffer of new wells before hydraulic fracturing.
The National Energy Technology Laboratory conducted high-resolution, helicopter magnetic surveys over four large land tracts in western and north-central Pennsylvania where historic oil and gas production has taken place and where unconventional oil and gas resource development is occurring or expected. The project's objective was to evaluate the ability of helicopter magnetic surveys to locate existing wells in heavily vegetated areas of varying terrain. Magnetic surveys locate wells by detecting the unique magnetic signature of vertical, steel well casing, which is depicted on magnetic maps as a "bull's eye" type anomaly centered directly over the well. To mitigate for the likelihood that wellbores exist where most or all casing has been removed, this study augmented helicopter magnetic data with supplemental information from farmline maps, state well databases, historic air photos, and digital terrain models generated from LiDAR datasets- all information that is publically available for areas within Pennsylvania.
The four surveyed areas include: 1) a 7 km2 (2.7 square mile) tract of privately owned land in Washington County with historic oil and gas production and where gas is now being produced from five, horizontal Marcellus Shale wells; 2) a 17.7 km2 (6.8 square mile) area of state owned land (Hillman State Park) in Washington County with historic oil and gas production and where the uppermost well casings were often cut off or buried by 1950's era surface coal mining; 3) a 28 km2 (10.8 square mile) block of state-owned land in the Susquehannock State Forest of Potter County where gas was once produced from the Oriskany Sandstone, but it is now a gas storage field; and 4) a 37.7 km2 (14.6 square mile) area of state owned land (Oil Creek State Park) in Venango County, which contains more than 900 known wells, including some of the oldest oil wells in the United States. Ground surveys to confirm well targets from the helicopter magnetic surveys have been completed for two of the four areas flown including: 1) the private land tract in Washington County, PA with Marcellus Shale development and 2) the area in Susquehannock State Forest that is now a gas storage field.
At the private land tract in Washington County, the helicopter magnetic survey identified 13 well-type magnetic anomalies within 1000 ft of the five horizontal Marcellus wells located there. The ground investigation confirmed that nine well-type magnetic anomalies were wells while four magnetic anomalies were found to arise from non well sources. One additional well with a weak (initially overlooked) magnetic anomaly was found using historical air photos. Of nine confirmed wells, six wells had recorded locations in Pennsylvania's statewide oil and gas wells database (PA*IRIS/WIS). However, the PA*IRIS/WIS locations were sometimes too inaccurate for the wells to be located in the dense underbrush.
At the gas storage field in Susquehannock State Forest, the helicopter magnetic survey identified 81 magnetic anomalies, including 55 well-type magnetic anomalies. A subsequent ground investigation confirmed that 30 of the 55 well-type magnetic anomalies were well locations. All confirmed wells except one were listed in the PA*IRIS/WIS state oil and gas well database and the locations provided were sufficiently accurate to locate the well in the field. The helicopter magnetic survey also identified two gas transmission pipelines with pulsed cathodic protection and multiple short pipeline segments without cathodic protection.
Helicopter magnetic surveys identified 192 well-type magnetic anomalies within Hillman State Park and 742 well- type magnetic anomalies within Oil Creek State Park. The ground investigation to confirm well locations in the two state parks had not commenced at the time of this report.
Preliminary observations from this study are: the PA*IRIS/WIS well database is incomplete for wells drilled between 1890 and 1920, the era of early well drilling at the Washington County Marcellus Area. Only six of nine confirmed wells were listed in this database. the PA*IRIS/WIS well database contained 29 of 30 wells found by the helicopter magnetic survey at the gas storage field in Susquehannock State Forest. Wells in this area were drilled post-1950 to produce from and store natural gas in the Oriskany Sandstone. This area contains active gas storage wells and plugged and abandoned gas wells. high resolution magnetic surveys acquired from low-flying aircraft provide accurate locations for wells with steel casing. However, wells with no steel casing exhibit weak or no magnetic anomaly. the inspection of publically available historic air photos or LiDAR imagery for well signatures can sometimes augment helicopter magnetic surveys by identifying well locations where the steel casing was recovered for reuse or salvage. complete casing strings are not needed for detection by helicopter magnetic survey although the minimum casing requirement for detection is not known.
the PA*IRIS/WIS well database is incomplete for wells drilled between 1890 and 1920, the era of early well drilling at the Washington County Marcellus Area. Only six of nine confirmed wells were listed in this database.
the PA*IRIS/WIS well database contained 29 of 30 wells found by the helicopter magnetic survey at the gas storage field in Susquehannock State Forest. Wells in this area were drilled post-1950 to produce from and store natural gas in the Oriskany Sandstone. This area contains active gas storage wells and plugged and abandoned gas wells.
high resolution magnetic surveys acquired from low-flying aircraft provide accurate locations for wells with steel casing. However, wells with no steel casing exhibit weak or no magnetic anomaly.
the inspection of publically available historic air photos or LiDAR imagery for well signatures can sometimes augment helicopter magnetic surveys by identifying well locations where the steel casing was recovered for reuse or salvage.
complete casing strings are not needed for detection by helicopter magnetic survey although the minimum casing requirement for detection is not known.