bluuebunny/crossref_metadata_2025_split huggingface dataset:
Higher Resolution Subsurface Imaging
Authors: Neal Jack , Krohn Chris 
Published: February 2015

R&D Grand Challenges - This is the fifth in a series of articles on the great challenges facing the oil and gas industry as outlined by the SPE Research and Development (R&D) Committee. The R&D challenges comprise broad upstream business needs: increasing recovery factors, in-situ molecular manipulation, carbon capture and sequestration, produced water management, higher resolution subsurface imaging of hydrocarbons, and the environment. The articles in this series examine each of these challenges in depth. The R&D Grand Challenges Series, comprising articles published in JPT during 2011 and 2012, is available as a collection on OnePetro (SPE-163061-JPT).
Introduction
It is hard to read road signs if you have poor eyesight, which is why driver’s licenses are issued with restrictions requiring that corrective lenses must be worn. Likewise, it is hard to find and exploit subsurface resources if you can’t clearly see your targets or monitor the movement of fluids in the reservoir.
Engineers now have powerful tools to precisely model subsurface reservoir production behavior, but a precise answer is still wrong if it is derived from an inaccurate subsurface description. Geoscientists make maps and rock property models of the subsurface by interpreting images that are produced from remote sensing data. Analogs from modern depositional environments and outcrop exposures guide subsurface data interpretation to predict ahead of the bit, then postdrill geostatistics are used to fill in stratigraphic details between wellbore control points. Selection of the right depositional model, facies distribution, and geostatistical analog depends on having the sharpest, most detailed and accurate image of the subsurface possible—the Grand Challenge of Higher Resolution Subsurface Imaging.
Over the past century, the industry has relentlessly sought ways to improve subsurface imaging of hydrocarbons. Canadian inventor Reginald Fessenden first patented the use of the seismic method to infer geology in 1917. A decade later, Schlumberger lowered an electric tool down a borehole in France to record the first well log. Today, advances in seismic and gravity data acquisition, electromagnetics, signal processing and modeling powered by high-performance computing, and the nanotechnology revolution are at the forefront of improved reservoir imaging.
In this paper, we will examine the challenges of getting higher resolution subsurface images of hydrocarbons and touch on emerging research trends and technologies aimed at delivering a more accurate reservoir picture.
Distributed Acoustic Sensing for Hydraulic- Fracturing Monitoring and Diagnostics
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 140561, ’First Downhole Application of Distributed Acoustic Sensing for Hydraulic-Fracturing Monitoring and Diagnostics,’ by M.M. Molenaar, SPE, Shell; D.J. Hill, QinetiQ OptaSense; and P. Webster, E. Fidan, SPE, and B. Birch, SPE, Shell, prepared for the 2011 SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, 24-26 January. The paper has not been peer reviewed.
Distributed acoustic sensing (DAS) is a fiber-optic technology that enables detecting, discriminating, and locating acoustic events with a standard telecom single-mode fiber several kilometers in length. Use of a combination of the measurement of backscattered light and advanced signal processing enables the DAS interrogator system to segregate the fiber into an array of individual “microphones.” One downhole application of DAS is monitoring hydraulic fracturing of tight-sand and shale-gas reservoirs.
Introduction
Fracture monitoring is key to understanding and optimizing hydraulic-fracturing treatments. The diagnostics focus on determining stimulation effects such as fracture geometry, proppant placement in the fracture, and fracture conductivity.
Historically, completion engineers have been limited to the use of surface wellhead rates and pressures, and occasionally downhole pressures, as their main sources of real-time information. To address such limitations, Shell Canada has been deploying distributed-temperature-sensing (DTS) systems in tight-sand and shale-gas wells for hydraulic-fracturing diagnostics.
The passive nature of fiber-optic sensors allows intervention- and interference-free operation. The inherent long-term reliability of such sensors, combined in a downhole-deployable single optical-fiber cable, makes fiber-optic technology an effective platform for permanent sensing in producing wells. DAS technology has potential for improvements in management of assets across the well’s life cycle, from exploration to operation.
Measuring Wellbore Acoustic Disturbances at the Surface
Surface Interrogator System. The DAS interrogator unit transforms a standard telecom (single-mode) fiber of sever-al kilometers in length into an array of microphones. This works because the interference of back-reflected laser light is affected by acoustic disturbances along the optical fiber. The technology can be deployed in new wells or used in most existing wells in which standard telecom optical fibers have been deployed for DTS purposes.
The DAS system uses a technique called coherent optical time-domain reflectometry, which involves the successive transmission of short pulses of highly coherent light down an optical fiber, and the observation of the very small levels of back-scattered signal caused by nonhomogeneities in the glass core. The system relies on sensing of vibro-acoustic disturbances in the vicinity of the fiber-optic cable.
Technology Focus: Production Operations (March 2012)
Authors: Alhanati Francisco J.S. 
Published: February 2015

Technology Focus
At the 2011 SPE Annual Technical Conference and Exhibition in Denver, there were many interesting discussions on shale-gas (and/or liquid-rich) resources. While already an important part of the industry, we are just beginning to identify some of the challenges with these resources and how best to deal with them. With hydraulic fracturing being an integral part of these operations, one area of focus is how to optimize the well geometry and the fracturing treatment to achieve long-term production and high ultimate recovery. Nevertheless, two other key considerations concern where to obtain the huge volumes of water that are required for these fracturing jobs, and what water treatment is required to ensure a safe and problem-free operation. With the need to rely less and less on fresh surface water to minimize the environmental effects, operators have been forced to explore other options, including finding suitable aquifers and/or water-recycling technologies. Some of the papers featured in this issue (or listed as additional reading) illustrate some of these challenges and how companies are trying to address them.
During this last year, we also saw an increase in the use of inflow-control devices in conjunction with horizontal wells in a variety of applications throughout the world. One of the most interesting developments is that of the so-called “autonomous” devices, which should be capable of adjusting themselves on basis of the type of fluid flowing through them (i.e., applying more choking to less-viscous fluids such as water and gas). There also have been interesting advancements in sandface-monitoring systems, as illustrated in two of the papers in the reading list.
Recommended additional reading at OnePetro: www.onepetro.org.
SPE 144032 A Novel Screening Method for Selection of Horizontal-Refracturing Candidates in Shale-Gas Reservoirs by Shekhar Sinha, SPE, Schlumberger, et al. (See JPT, November 2011, page 102.)
SPE 147264 Shale-Gas Water-Treatment Value Chain—A Review of Technologies, Including Case Studies by Patrick Horner, Aqua Pure Ventures, et al.
SPE 145737 The Autonomous RCP Valve—New Technology for Inflow Control in Horizontal Wells by Vidar Mathiesen, Statoil ASA, et al.
SPE 147439 Fiber-Optic Strain Sensing at the Sandface Enables Real-Time Flow Monitoring and Compaction Mitigation in Openhole Applications by Denise M. Earles, SPE, Baker Hughes, et al.
SPE 145581 Ormen Lange: Delivering Production Optimization and an Improved Reservoir Understanding Using a New Cableless Sandface-Monitoring System by B.P. Champion, SPE, Expro, et al.
4D Seismic for Reservoir Management in Carbonates: Does It Work?
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 144228, ’Application of 4D Seismic for Reservoir Management in Carbonates: Does It Work?,’ by Mohamed Saleh Efnik, SPE, and Samsudin Haj Taib, University of Malaya, prepared for the 2011 SPE Enhanced Oil Recovery Conference, Kuala Lumpur, 19-21 July. The paper has not been peer reviewed.
In the past 10 years, time-lapse (4D) seismic has evolved from an academic research topic to a typical method of monitoring reservoir performance. The method is used to provide evidence of saturation changes within the reservoir at field scale. 4D seismic provides data that describe the dynamic behavior of reservoir fluid between wells that otherwise would be limited to small-scale monitoring at borehole scale. Thus, 4D seismic provides sophisticated techniques of reservoir monitoring and management that rely on the integration of geological models, static and dynamic properties of the reservoir rock, and detailed field-production and -pressure data.
Introduction
The feasibility of 4D seismic has evolved with studies that showed that certain rock properties, such as acoustics and pressure, are affected by changes caused by hydrocarbon production over the life of the field. The use of 4D-seismic data in conjunction with reservoir-simulation models and production data enables creation of an internally consistent subsurface model. It has been shown that acoustic impedance (AI) and Poisson’s ratio are related closely to porosity and water-saturation changes in Arne chalks. An increase in porosity causes a decrease in AI; increasing water saturation (at constant porosity) results in a strong increase in Poisson’s ratio.
An extensive seismic program was carried out over a CO2-injection area during a 5-year span to monitor the CO2 storage in a saline aquifer in the North Sea Utsira sand. 4D seismic and other geo-physical techniques were used to obtain information that could help determine reservoir-quality characteristics and predict fluid contacts. Forward modeling of 4D seismic has been shown to be a useful reservoir-management tool. Here, the simulation model was combined with the streamline method for modeling flow, and the ray-Born method for synthetic seismograms was used to compensate for the numerically expensive model because of the large volumes in the subsurface.
Forties Infill Drilling 8 Years Later: Development Driven by 4D Seismic
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 145433, ’Forties Infill Drilling 8 Years On: Continued Success Through the Application of Thorough Development Geoscience Driven by 4D Seismic,’ by Philip Rose, Gregg Barker, Klaas Koster, and Jeff Pyle, Apache North Sea, prepared for the 2011 SPE Offshore Europe Oil and Gas Conference and Exhibition, Aberdeen, 6-8 September. The paper has not been peer reviewed.
In the 8 years since Apache purchased the Forties field, more than 100 in-field targets have been drilled, with an overall success rate of 74%. The campaign resulted in a shortage of sidetrack-donor wells, with a return to surface drilling on all five platforms. To enable full exploitation of the target portfolio, Apache is installing a new 18-slot platform in 2012. Key to success has been a constant drive to push the boundaries of 4D-seismic interpretation and of the lithology prediction from seismic, and the ability to integrate this information with local production and well data.
Introduction
The Forties field, in the UK central North Sea, was purchased by Apache in 2003, at which time it was a giant field in the decline phase of its life. Annualized average production was 41,000 BOPD and declining. No new wells had been drilled in the field since 2001. In the early 1980s, the field produced between 400,000 and 500,000 BOPD. By 2003, the field had produced 2.5 billion bbl of the 4.2- to 5-billion-bbl original oil in place. The field’s remaining recoverable reserves were listed as 144 million BO. Since the purchase, more than 100 drilling targets have been tested, resulting in more than 80 production and four injection completions. As a result of the drilling campaign, annualized average production has remained at approximately 60,000 BOPD since 2005, with total production of more than 150 million BO, of which 75 million BO has been produced from newly drilled wells. As shown in Fig. 1, approximately 70% of the current field production is from wells drilled since the purchase.
Foundation: Data Integration
Use of an integrated multidisciplinary interpretation approach was critical to identify new targets continually. The ability to display well-log-derived attributes with seismic amplitudes, seismic geobodies, and production information in a single interpretation environment was invaluable. The data book contains map locations, illustrations of the pay section with completion history, production history, workover record, and a current completion diagram for every well completed in the field. All interpreters have access to the company’s live production-allocation database. Although many of the infill-drilling targets were driven by seismic interpretation, including the identification of direct hydrocarbon indicators (DHIs) or unswept areas highlighted by time-lapse (4D) seismic, others were generated to replace mechanically failed wells having remaining production potential, and a few targets were generated following the analysis of simulation results.
Innovation: Taking Charge of Completion Innovations
Authors: Imomoh Egbert 
Published: February 2015

President's column
The essence of most drilling operations in our industry is to open the maximum length of reservoir formation with the mini-mum damage to the rock surface. This should allow maximum efficient flow of the desired reservoir fluids into the wellbore and to the surface. The proper completion of a well will ensure that production is not denied or restricted, and enough care is taken to ensure that all the investment made in drilling the well is safeguarded. The term “completion” covers a gamut of activities related to stopping the movement of wellbore material into the well, the running of tubing and attachments needed to flow the reservoir fluids to the surface safely, the installation of subsurface equipment to increase production, and to provide well protection. One short article will not be adequate to do justice to this very important element of providing energy for the world.
My first experience with well completions was in the Niger delta where the producing formation is friable sandstone, which is prone to dislodgement when production commences. We used a mixture of sand consolidation chemicals to “glue” the sand matrix through perforations in the production casing. The process required preparation of chemicals at the surface properly tailored to the prevailing temperature and pumped into the selected part of the pay zone. The placement had to be very accurate, as any unconsolidated part of the open reservoir could play havoc with production and surface equipment after the well was brought into production. These wells were relatively simple, as they were vertical and shallow.
Since the first wells were brought into production, a number of completion innovations have been introduced that have permitted the safe and profitable production of oil and gas. Some of them are now routinely used and their process of evolution is now buried in history. Today’s wells are in general much deeper and more complex and therefore have benefitted from innovation to ensure maximum inflow per length of reservoir. Operators carefully choose the form of completion that best suits the formation—including gravel packs, open hole, and multizone, to name a few.
Comments: HSE Now
Authors: Donnelly John 
Published: February 2015

Editor's column
This month, SPE will launch a new web- and app-based publication focusing on the health, safety, security, environment, and social responsibility (HSSE-SR) discipline. With news, updates, and technical information needed by oil and gas professionals working in this discipline, HSE Now will be updated continually and will be available on the web and mobile devices such as tablets and smartphones. It will be free to all SPE members.
Unlike other SPE publications, HSE Now will include articles, reports, government documents, and other material from both SPE and non-SPE resources around the globe. The amount of information in this area has exploded in the past decade as the oil and gas industry is being held to higher standards in areas such as environ-mental responsibility, sustainability, and workplace safety. The occurrence of high-profile accidents such as the US Gulf of Mexico Macondo explosion has heightened public scrutiny of industry standards and practices.
The new periodical also reflects an outreach by SPE to a group within the industry that does not have an obvious professional home. Last year, SPE launched a print publication, Oil and Gas Facilities, targeted to the increasingly important projects, facilities, and construction discipline and the publication has been very well received. The primary objective is to make it easier for SPE members working in this discipline to find critical information they need to do their jobs. Because the subtopics in this discipline are so diverse, there is no single source of information on the collective topic, and the SPE vehicle will serve as a curator of information, bringing together high-quality SPE and non-SPE information on the discipline.
An editorial advisory board will help HSE Now plan and develop content. Its members are Roland Moreau, ExxonMobil, chairman and SPE Technical Director for Health, Safety, Security, Environment, and Social Responsibility; Tom Knode, Halliburton; Emmanuel Garland, Total; Herman Vacca, EP Energy; Davide Scotti, Saipem; Dave McLeod, Halliburton; Mark Whittenberg, Schlumberger; Chris Deepak, Halliburton; Clarion Johnson, ExxonMobil; Andrew Wojtanowicz, Louisiana State University.
Moreau describes the increasing importance of HSSE-SR in the industry in this month’s Guest Editorial. Operators, service companies, and others involved in producing oil and gas to meet growing global demand are challenged today to do so safely and in a way that is compatible with the environmental and economic needs of local communities.
SPE is also meeting the demand for more information and dialogue in this area through a growing number of regional HSSE-SR conferences around the world, in addition to workshops and on-demand web events. This month, an SPE Americas HSSR-SR conference will take place in Galveston, Texas, and similar conferences are scheduled this year in London, Lima, and Doha. The SPE International Conference on Health, Safety, and Environment will be held in March 2014 in Long Beach, California.
At-Bit Inclination, Gamma, and Imaging System Tracks Productive Zone in Complex Geology
Authors: Flook Robert , Alexander Will , List Dave , Sencenbaugh Bob , Enoch Breck , Wheeler Aaron J. , Starkey Allen , Rennie Allan 
Published: February 2015

Technology Update
In unconventional resource plays and fields with structural or stratigraphic complexities, reliable geosteering of horizontal laterals is essential to economic success. Each foot drilled out of zone represents a potential loss of production revenue. Using real-time logging-while-drilling (LWD) data can reduce directional drilling risk. However, conventional bed boundary imaging tools are typically located far behind the drill bit. This creates a significant lag in response time and increases the odds of exiting the target interval.
The recent introduction of an at-bit inclination, gamma ray, and imaging technology has enabled Fidelity Exploration & Production to optimize well placement in a target formation of the Para-dox Basin in Utah—despite unexpected faults and local changes in formation dip that were not clearly resolved with seismic data.
The Geological Challenge
During the Pennsylvanian period, the Paradox Basin was rapidly subsiding and filling with thick, cyclic sequences of marine carbonates, evaporates, silts, and shales. Relatively thin, reservoir-quality clastic and carbonate formations became interbedded within organic-rich shales, surrounded by thick salt deposits. Salt above and below these self-sourced oil and natural gas reservoirs provides critical sealing capacity, while preserving overpressures generated during hydrocarbon maturation. However, the thick-nesses of potential reservoirs vary as a result of syndepositional faulting and subsequent salt movement, dissolution, and collapse. Many exhibit open, near-vertical fractures controlled by regional tectonics and local folding because of salt flows over anticlines and underlying fault blocks.
Local thickness variations, folding, and subseismic faulting of Paradox reservoirs have presented significant challenges to operators. One target interval, a dolomite-silica silt reservoir enclosed in a fractured and overpressured shale formation, averages 40-ft thickness in southwestern Utah.
Drilling activity there has undergone two distinct phases, with varying degrees of success. The first phase, from the 1960s through the early 1980s, included the drilling and completion of almost a dozen vertical wells. One well was an economic success, producing more than 1 million bbl of oil and establishing the formation’s potential. Horizontal drilling, introduced in the early 1990s, increased the probability of encountering natural fractures that influence production. Roughly half of these wells produced commercial oil, including one that has yielded more than 600,000 bbl to date.