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SPE/EAGE European Unconventional Resources Conference & Exhibition - From Potential to Production
- Conference date: 20 Mar 2012 - 22 Mar 2012
- Location: Vienna, Austria
- Published: 20 March 2012
61 - 74 of 74 results
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Non-Conventional Plays in Romania: the Experience of OMV Petrom
Authors Csaba KREZSEK, Simon LANGE, Radu OLARU, Cristina UNGUREANU, Pervin NAMAZ, Roxana DUDUS and Valentin TURIThis paper describes the key findings of a regional study that targeted the unconventional potential of exploration assets hold by OMV Petrom in Romania. Three unconventional plays have been evaluated, including the (1) Silurian and (2) the Dogger on the East European Margin (including Moesia), and the (3) Oligocene in Maramures (Pienides). The Silurian shales are at 2- 4 km depth in the gas window on Western-Central Moesia. Maturity in most cases has been reached by the Late Paleozoic and it was followed by significant exhumation during the Hercynian Orogeny. The quality of Silurian shale represents a major uncertainty, due to the sparse dataset represented by old wells. The Dogger shales of Northern Moesia are in the oil and gas window under the most external thrusts of the Carpathians at depths that exceed 4 km. The shales have TOC values up to 6 %. Oligocene shales with TOC of up to 10 % in Maramures are in the oil window at depths of less than 2 km. This makes them a very attractive target for shale-oil exploration. However, major setbacks are the complex tectonic structure, rugged topography and large-scale exhumation. Ongoing exploration efforts for non-conventional plays are targeted to define the mechanical properties and the exploration sweet spots in the above mentioned plays, but also assessing the potential of the Late Paleozoic bituminous dolomites of Moesia and other black shales in the Carpathians.
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Validation of Surface and Shallow Microseismic Array for Deep Reservoir Monitoring
Authors Anca Rosca and Christophe MaisonsMonitoring reservoir stimulation operations provides data for predicting production performance and for reservoir characterization but also, potentially, for compliance with local regulations. With improved drilling and completion technology the depth of the unconventional reservoirs produced increases and the options for deploying cost–effective microseismic monitoring equipment become limited. The monitoring technology has to adapt by optimizing acquisition geometry and data processing as well as the procedures that demonstrate the validity of the results. A practical solution for microseismic monitoring of stimulation operations in an unconventional reservoir under development is a surface or shallow distributed array. We are analyzing three such datasets together with complementary deep borehole sensor datasets to understand how to predict and validate the expected performance of distributed surface and shallow arrays. The surface recorded data is processed by stacking and event detection and location are accepted based on statistical criteria. This catalog of events is compared to the one obtained from borehole array where waveforms can be analyzed individually in order to validate the quality of event analysis.
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Identifying Fault Activation in Unconventional Reservoirs in Real Time Using Microseismic Monitoring
Authors Michael Kratz, Andrew Hill and Scott WesselsIdentification of fault related microseismicity in hydraulic fracture treatments is crucial to understanding how treatments are stimulating a reservoir. Evaluating b values in combination with event source mechanism provides a reliable and intuitive method for separating fault related microseismic events from standard fracture related events. Typically this analysis is conducted after a treatment is complete and serves as a diagnostic tool to provide possible explanations for reduced production or designing future treatments on nearby wells to avoid an identified fault feature. Being able to identify such features in real time allows the operator to not only identify faults but to stop treatment and avoid these features all together saving time and materials that would otherwise be pumped into an area that doesn’t contribute to the overall stimulation of the reservoir, and could reduce production on the well. When evaluating b-values in real time, a technique that can identify faulting early in the initiation of fault stimulation is crucial for preserving the most resources during treatment.
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Reserves and Performance Comparisons of Multi-Fractured Spearfish Horizontal Wells, to Various Fracturing Techniques and Well Spacing Configurations
More LessThe light oil bearing, low permeability, Spearfish formation, in Southwest Manitoba, Canada, has been a recent target of extensive horizontal drilling and fracture stimulation. An extensive completion database, along with historical production data, is available in the public domain. It is beneficial to review what the production trends illustrate about this play, in order to optimize the development of other similar types of low permeability sandstone plays, with regards to horizontal well spacing and fracture design. Decline analysis was performed on over 120 horizontal wells that had sufficient completion information available, to study the effects of varying fracture spacing and size. The emphasis was to review the longer term production histories of the oil wells, as well as the predicted ultimate reserves, and see if there were any discernible trends, when production was compared to various fracture parameters. Both the initial production rates and the ultimate reserves, showed significant data scatter when compared with fracture size, and number of fractures per well. It was difficult to make strong conclusions about initial production rates, being a function of varying fracture parameters. Closer analysis of individual wells, suggests that ultimate reserves appears related to the moveable oil-in-place, within the drainage area that a horizontal well produces from. It appears that well spacing effects and localized reservoir properties, must be taken into consideration, when analyzing the long-term performance of multi-fractured horizontal wells. It seems that caution is required, when drawing long-term conclusions from initial production results. The basic reservoir engineering principle of an oil well draining a defined reservoir volume, are still applicable to low permeability reservoirs. There appears to be a finite number of horizontal wells that can be drilled in any given area, and an optimum number of fracture stimulations that can be placed per well.
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Lessons Learned from North America and Current Status of Unconventional Gas Exploration and Exploitation in China
Authors Ping Wang, Ruizhong Jiang and Shichao WangUnconventional gas has been paid more and more attention since the successful exploration in North America, China is no exception. Effective exploitation of unconventional gas can guarantee energy security, optimize energy structure and help protect environment in China. Successful experiences from North America are summarized, current status of unconventional gas in China is analyzed from three aspects: resources, technologies, polices. The success of North America profits from five reasons: governmental positive policies and tax preferences, advanced technologies, adequate pipeline infrastructure, small firms leading system, large demand of natural gas. China has large potential resources of unconventional gas. As to tight gas, the prospective resources of tight gas exceed 12 trillion cubic meters. For coal-bed methane(CBM), China is ranked 3rd after Russia and Canada and has 36.8 trillion cubic meters. China has just started shale gas study and has no definite evaluation. Until now, China has developed a series of technologies. For tight gas: high-precision 2D seismic, fast drilling, slim hole drilling. As for CBM: AVO response detect, penniform multi-lateral drilling and ultra-short radius jetting drilling. China has set many beneficial policies for unconventional gas especially for CBM, now the government is working hard on making positive policies and tax preferences for shale gas. There are several differences between North America and China: geological difference, land ownership, regulatory framework, pipeline network, small firms in America and national oil companies in China. Some suggestions are proposed for China: set positive policies and tax preferences, develop advanced and adaptive technologies, consummate natural gas market system and infrastructure, cooperate with foreign companies and monitor the effect of unconventional gas exploitation on environment. These summaries and suggestions can be instructive for other countries to develop unconventional gas.
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Production Data Analysis in Eagle Ford Shale Gas Reservoir
Authors Bingxiang Xu, Manouchehr Haghighi and Dennis Cookeve analysis technology to analyse the production behaviour and to estimate the essential parameters for this reservoir. This type curve was constructed based on transient production rate with constant well pressure in a closed boundary of stimulated reservoir volume (SRV) with double porosity approach. In order to analyse the early production data we used Bello’s and Nobakht’s approach to account for apparent skin. In this study, three flow regimes were identified consisting of 1- bilinear flow; 2- matrix linear flow; and 3- boundary dominated flow. For the analysis of early flow regime, two possibilities of transition flow and apparent skin have been considered. First, the fracture permeability was estimated to be around 820 nano Darcy based on transition flow analysis. Second, the matrix permeability was estimated to be either 181 or 255 nano Darcy based on two different approaches in matrix linear flow regime. Furthermore, original gas in place (OGIP) and SRV were estimated from the boundary dominated flow regime. To validate the estimated matrix permeability, a single porosity numerical model with high permeability transverse fractures was built to match the production history. The permeability from simulation was in a good agreement with type curve analysis. Production forecasting has also been carried out using different adsorption isotherms. The results showed that the effect of desorption depends on the reservoir pressure and the shape of adsorption isotherm curve. In early time of production, desorption is usually not effective, however, for long-term production forecasting, it is necessary to account for this phenomenon by providing an accurate isotherm
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Cyclic Shut-in Eliminates Liquid-Loading in Gas Wells
Authors Curtis Hays Whitson, Silvya Dewi Rahmawati and Aleksander JuellThis paper presents a method to eliminate production loss due to liquid-loading in tight gas wells. Cyclic shut-in control is a simple production strategy that particularly benefits lower-permeability stimulated wells, including but not limited to shale gas wells. Comparison is made between a gas well producing (1) in a “ideal” situation where 100% of liquids entering from the reservoir or condensing in the tubing are continuously removed (without shut-ins), (2) in a meta-stable liquid-loading condition with low gas rate, typical of most wells today, and (3) by the proposed strategy of cyclic shut-in control. We show that cyclic shutin control of stimulated low-permeability vertical wells to ultra-low-permeability horizontal multi-fraced wells can produce without ever experiencing liquid loading, and with little-to-no delay of ultimate recovery. Cyclic shut-in control can be applied to all stimulated, lower-permeability gas wells, from the onset of gas rates that result in liquid-loading. The strategy can also be used for wells which already have experienced a period of liquid-loading , but the expected performance improvement may be less because of near-well formation damage caused by historic liquid-loading – e.g. fresh-water backflow and liquid-bank accumulation. In historically liquid-loading wells, an initial period of liquid removal and/or light stimulation may be needed prior to initiating cyclic shut-in control. We show that the shut-in period should optimally be as short as operationally possible. Cyclic shut-in control is shown to work equally well for layered no-crossflow systems with significant differential depletion at the onset of liquid loading. Minimizing rate and recovery loss of liquid-loading gas wells is of international interest. We believe that cyclic shut-in control will become an industry standard practice for shale gas wells, and should lead to a significant ultimate increase in worldwide gas reserves. The method is extremely simple and requires only a rate-controlled wellhead shut-in device.
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Selection Criteria for Tubular Connection used for Shale and Tight Gas Applications
Authors Catalin Teodoriu and Tu ClausthalAn unconventional reservoir poses not only difficulties in producing it economically but also requires constrains about the well construction and tubular selection in order to keep the budget in acceptable limits. The tubular used for well construction and well completion must offer maximum integrity at, if possible, minimum costs for the life of the well. The costs associated with tubular are generated by the steel price plus the connection costs. Use of premium connections may not be justified in all unconventional reservoir applications, but as this study will prove, they offer better solutions when the life if the well is considered. This paper starts with a review of main tight gas fields worldwide and based on the well analysis a general tendency for well completion will be shown. The second part of the work will focus in analyzing casing design criteria used in afore mentioned fields. As a result a comprehensive discussion about casing and coupling selection for unconventional wells will be generated. Premium versus non premium connections will be discussed and their impact on the life of the well will be analyzed.
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Identification, Integration and Upscaling of Mudrock Types - A Pathway to Unlocking Shale Plays
Authors Joan M. Spaw and Marathon Oil CompanyA multidisciplinary approach to shale characterization in a variety of North American gas- and liquids-rich shale plays has lead to improved understanding of the bulk physical, chemical and mechanical properties of these deposits and their geologic history. This effort is leading to successful exploitation of these enigmatic resources. Microfacies analysis of mudrocks provides a platform for upscaling from the “nano” to the regional scale, and results in comprehensive mudrock characterizations. Microfacies analysis of mudrock types within a select stratigraphic interval in a basin leads to the recognition of mudrock lithofacies. Lithofacies identification allows for calibration of petrophysical models, documentation of basinspecific variations in mudrock composition and microfabrics, the distribution of organic-rich members of these intervals, definition of the mechanical stratigraphy for completion design, and provides the litho-stratigraphic building blocks for predictive sequence stratigraphic models. Successful exploration and exploitation of mudrocks as resources can be advanced when the recognition of mudrock lithofacies provides a methodical means to tie together the geologic, chronostratigraphic, geochemical and petrophysical data from a diverse spectrum of physical scales and technical disciplines.
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Just-In-Time Perforating for Controlled, Cost-Effective Stimulation and Production Uplift of Unconventional Reservoirs
Authors Renzo Angeles, Randy Tolman, Wadood El-Rabaa, Shalawn Jackson and Kris NygaardRecent advances in multi-stage stimulation technologies, including open- and cased-hole types, have largely overlooked the advantages of single-zone stimulation due to hardware and cost limitations. In most conventional methods, multiple perf clusters are treated at once using one single frac stage with the expectation that equally-stimulated fractures will be created at each perf cluster within tens and hundreds of feet. This creates over-stimulation in some perf clusters and under-stimulation in others, which unveils the current economic and practical limits of effectively creating fractures where needed, not where it is possible to place them. Other methods use a large number of frac plugs which require additional wireline trips and later need to be drilled out, increasing the total cost and mechanical risk of the completion. As lateral length increases, many operators also face the challenge of not being able to remove all frac plugs due to coiled-tubing depth limitations. This paper introduces the recent implementation of Just-In-Time Perforating (JITP) in shale gas, unconventional plays. JITP is one of the Multi-Zone Stimulation Technologies (MZST) developed and patented by ExxonMobil over a decade ago and extensively used in vertical and S-shaped wells in the Piceance basin, Colorado, and recently implemented in the XTO Fayetteville Shale, Arkansas. JITP creates multiple single-zone fracture stimulations on a single wireline run using ball-sealer diversion and perforating guns that remain downhole during fracturing. Other key features of this method are the use of less horse power, significant reduction in the number of frac plugs, fewer wireline runs, and added flexibility in water management. This paper describes the technical advantages and business justification for applying JITP in unconventional resources and also provides preliminary results from the performance of the JITP field trials in horizontal wells.
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Assessment of SAGD Well Configuration Optimization in Lloydminster Heavy Oil Reserve
Authors M. Tavallali, B. Maini, T. Harding and B. BusahminLarge quantity of heavy oil resources are present in variety of complex thin reservoirs in Lloydminster area which are situated in east-central Alberta and west-central Saskatchewan. Primary depletion and waterflooding are the principal recovery techniques. Although these techniques work, the recovery factors remain low and large volumes of oil are left unrecovered when these methods have been exhausted. Because of the large quantities of sand production, many of these reservoirs end up with a network of wormholes that makes most of the displacement type enhanced oil recovery techniques inapplicable. Because of these high conductivity channels, only gravity drainage based techniques have a good chance of success. Among the applicable methods in Lloydminster area, SAGD has not received adequate attention, mostly due to the notion that heat loss in thin reservoirs would make the process uneconomical. While this may be true, the limiting reservoir thickness for SAGD under varying conditions has not been established. These reservoirs contain light oil with sufficient mobility. Therefore the communication between the SAGD well pairs is no longer a hurdle. This opens up the possibility of increasing the distance between the two wells and introducing elements of steamflooding into the process in order to compensate for the small thickness of the reservoir. The main objective of this study was to evaluate the effect of well configuration on SAGD performance and develop a methodology for enhancement of the SAGD performance through optimizing the well configurations for Lloydminster type of reservoir. A new well configuration was able to significantly improve the application of SAGD in thin reservoirs of Lloydminster. It provided high RF at reasonable cSOR. The effects of some common Lloydminster reservoir characteristics, which are problematic for the SAGD process (such as initial gas saturation, bottom water, and gas-cap) were investigated for the most promising well configuration
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An Environmental Solution to Help Reduce Freshwater Demands and Minimize Chemical Use
Authors Jason E. Bryant and Johanna HaggstromNew technologies to reduce chemical exposure to personnel and the environment during fracturing operations are at the forefront of research and development efforts. Unconventional reservoir developments require large amounts of fresh water, sometimes up to 5 million gal to complete a well, leading to difficulty in water sourcing in remote locations or regions where droughts are persistent. Several new areas currently under consideration for shale exploration are in environmentally sensitive locations, making the water sourcing for fracturing operations even more critical. Freshwater use needs to be minimized, and a careful examination of current practices should be undertaken to reduce, eliminate, and recycle chemicals wherever possible. Furthermore, fracturing fluids essential for successful stimulation treatment should be comprised of chemicals adhering to environmentally acceptable standards. Recent developments have allowed one operator to minimize freshwater usage through recycling of their flowback and produced water using electrocoagulation (EC) technology. EC is a water-treatment process that removes colloidal solids through methods of coagulation, electroflotation, and settling. Unlike conventional water-treatment practices, such as reverse osmosis or distillation, EC generates relatively small quantities of waste, while leaving dissolved solids in the water. To ensure enough water was available for fracturing stimulation treatment, fresh make-up water was also used. This freshwater source was treated for bacteria using an ultraviolet (UV) trailer, which minimized the need for biocide on location. In addition, dry-blending technology was used to hydrate the gel without the aid of mineral oils. All of these processes were used to reduce the environmental impact on location. With increasing public scrutiny and concern over the practice of hydraulic fracturing in environmentally sensitive locations, fluid systems need to follow strict environmental guidelines. A new fluid system was developed with components from the US Code of Federal Regulations Title 21 (CFR 21), or the Generally Recognized as Safe (GRAS) affirmation process. While setting a high precedence by adhering to this environmental benchmark, the fluid performance was not compromised.
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European Shale Gas, Getting Buy-in From the Public and Stakeholders
Authors Mark A. Miller and Eric VaughanDuring the past 10 years shale gas development projects have proven to be highly successful in a number of North American basins, and have become a game changer for the energy supply there. Because of these successes, shale gas exploration and development technologies are being deployed around the globe, including Europe. But while there appears to be vast shale gas resources across Europe, many industry analysts express concerns about the probability of repeating the North American successes in Europe. These concerns are based on the denser population in Europe, different safety and environmental regulations, and the doubts of many European residents about the overall safety of shale gas development. Moreover, unlike North America where landowners often are entitled to significant lease payments and royalties for their mineral rights, the mineral rights throughout most of Europe are owned by the governments, rather than the landowners. The combination of these factors adds to the difficulty of building public support for a shale gas program. This paper provides a discussion of a shale gas exploration program currently being conducted by Cuadrilla Resources in England. It examines the concerns of the local residents, and how these have affected media coverage, and support (or opposition) from politicians. It discusses the strategy and approach used by Cuadrilla for addressing questions and concerns from the local residents, various UK regulatory bodies, politicians and the media. While this paper focuses on a UK shale gas case, the conclusions and recommendations are applicable to any shale gas program in Europe or elsewhere.
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Water Management – An Increasing Trend in the Oil and Gas Industry
Authors Freeman Hill, Steve Monroe and Reshmy MohananWater plays an essential role in the recovery of oil and gas. Managing subsurface water conformance can maximize hydrocarbon production and reduce operating costs. However, unchecked water can decrease hydrocarbon production, reduce oil and gas recovery, increase costs substantially, and lead to possible well abandonment. In the life of a well it is natural that water will eventually enter into the production stream. It is important to identify the water’s source and reason for the intrusion, and how it is interacting with the wellbore. This knowledge can be used to create an integrated customized solution that fits the needs of the well. An indepth understanding of the reservoir can avoid water problem areas in new infield drilling by the use of advanced navigation and directional systems. Water management is essential to maximizing returns on investment and in controlling costs. There are a variety of technologies available for near-wellbore control and reservoir water conformance. Understanding of the water mechanism followed by proper application is key to reducing excess water production.
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