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A common horizontal well completion design, in recent times, in tight gas reservoirs includes the ability to place multiple hydraulic fractures along the length of the wellbore. This practice provides a better drainage pattern and the required flow capacities for the gas to flow making tight gas reservoirs economically viable producers. This is the customary completion practice for clastic rock development, which has shown good results. However, in many cases especially when stepping out in regions beyond the established boundaries, completion design by itself is not sufficient to ensure desired production. The standard protocol to get the best chance of placing the horizontal section in good quality reservoir is to first perform petrophysical evaluation of the preferred pay interval, drill a pilot hole through the potential reservoir section and then place the lateral section in the zone of interest. The pilot hole provides a control point and helps reduce uncertainties in drilling laterally through the target pay zone.This typical completion procedure however does not guarantee identical production even in offset wells. In a conceptual case where two offset wells(A & B) with similar pilot hole petrophysical attributes drilled horizontally in the same maximum horizontal stress direction but in diagonally opposite azimuths produce at widely differing rates. Uncertainties in far-field geology, areal limits, pore pressure distribution, rock property distribution, etc.are well known challenges that can contribute to making well delivery predictions difficult. To help in such situations and better understand the differences in well behavior a detailed workflow based study that includes reservoir characterization, well placement, stimulation design and production history matching is required. The objective of such a study would be to address questions regarding reservoir quality and identifiable "sweet spots," the absence of which could result in poor well performance. The workflow study discussed here is a review of well accepted practices with the objective of highlighting challenges and providing insights into the best and most effective ways to develop complex and highly heterogeneous plays. The workflow loop (Figure 1) is an iterative study process where well performance puts the final seal of approval on the pre-job modeling and executionplanin the well delivery process. In cases where the wells fall below expectations the iterative loop would look for additional information to refine the earlier assumptions. This study considers examples where palynology helped improve geological understanding and played a critical role. The workflow sequence is mapped in this paper.
A common horizontal well completion design, in recent times, in tight gas reservoirs includes the ability to place multiple hydraulic fractures along the length of the wellbore. This practice provides a better drainage pattern and the required flow capacities for the gas to flow making tight gas reservoirs economically viable producers. This is the customary completion practice for clastic rock development, which has shown good results. However, in many cases especially when stepping out in regions beyond the established boundaries, completion design by itself is not sufficient to ensure desired production. The standard protocol to get the best chance of placing the horizontal section in good quality reservoir is to first perform petrophysical evaluation of the preferred pay interval, drill a pilot hole through the potential reservoir section and then place the lateral section in the zone of interest. The pilot hole provides a control point and helps reduce uncertainties in drilling laterally through the target pay zone.This typical completion procedure however does not guarantee identical production even in offset wells. In a conceptual case where two offset wells(A & B) with similar pilot hole petrophysical attributes drilled horizontally in the same maximum horizontal stress direction but in diagonally opposite azimuths produce at widely differing rates. Uncertainties in far-field geology, areal limits, pore pressure distribution, rock property distribution, etc.are well known challenges that can contribute to making well delivery predictions difficult. To help in such situations and better understand the differences in well behavior a detailed workflow based study that includes reservoir characterization, well placement, stimulation design and production history matching is required. The objective of such a study would be to address questions regarding reservoir quality and identifiable "sweet spots," the absence of which could result in poor well performance. The workflow study discussed here is a review of well accepted practices with the objective of highlighting challenges and providing insights into the best and most effective ways to develop complex and highly heterogeneous plays. The workflow loop (Figure 1) is an iterative study process where well performance puts the final seal of approval on the pre-job modeling and executionplanin the well delivery process. In cases where the wells fall below expectations the iterative loop would look for additional information to refine the earlier assumptions. This study considers examples where palynology helped improve geological understanding and played a critical role. The workflow sequence is mapped in this paper.
Modern logical information and control models are the brains that run, monitor, maintain and secure operational facilities. The design objective of these logical systems is to optimize production and performance while minimizing supply chain problems. To achieve this critical objective, information flow, critical data, operational control points, as well as risk points are identified while fitting together the different compartments of these artificial models. This cyber and logical representation of the physical asset environments, such as drilling and workover rigs, is displacing the traditional physical operational models in several domains of the oil and gas industry, including upstream, midstream and downstream. With the extended, geographically dispersed infrastructures of the oil and gas industry, the real-time communication and remote control capabilities are providing privileges to make more robust decisions that optimize deliverables. Additionally, as the added technologies, such as surveillance, are replacing the human element in tough locations, safety records are being boosted by reducing exposure to combustible, harming chemicals and off-road traffic. Automation is often more efficient and safer than human intervention because it offers new operational capabilities, such as forward prediction, swift detection and reaction to events, and shuts down immediately if anomalous activities are indicated in data flow patterns or if signals are lost. For instance, onshore and offshore drilling operations in real-time monitoring and control centers that run land and subsea operations apart from the control room rely on analytics-driven strategies provided by the adopted intelligent systems to harness the full value of operational excellence. This paper explores the design and function of the logical cyber representation of the physical asset environments, whether for drilling wells, producing wells, pipelines, or treatment facilities, to list a few components of the oil and gas supply chain. Physical assets and their controls are different for each compartment, and so are the communication networks and accompanying proprietary software. There are distinctive characteristics for each logical information and control network deployment architecture, depending on the operational requirements and levels of tolerance. This paper also highlights examples where such models have promoted solutions to mitigate uncertainty. For example, forward pore pressure prediction was applied while drilling along the minimum in-situ horizontal stress plane to predict what is ahead of the bit, improve wellbore stability and lateral trajectories, validate data, and prevent human error. The analysis conducted showed that operational efficiency and cybersecurity compromise is essential for business success while constructing the information and control models. The paper discusses three useful tools that assist in promoting integrated cybersecurity for artificial models. The three tools are safety instrumented systems, decision tree, and information risk management.
Horizontal drilling and completion advances in tight gas and shales have allowed access to significant new resources both in existing fields and new plays. Open hole multi-stage fracturing (MSF) technologies using ball operated sleeves and openhole packers have generally been effective in delivering high productivity wells, worldwide. Successful case histories treating tight shale gas with MSF completions abound in current literature, however, it is important to note that a majority of these case histories deal with reservoirs with high pressures. Often tight gas reservoirs are initially found to be over-pressured (higher than water gradient), but as with all depletion drive systems, the reservoir pressure depletes with the removal of fluids. Pressure depletion brings along with it its own set of challenges. The wells cease to have the ability to flow naturally to surface, liquid loading, and artificial lift are issues that come to the forefront. Conventional multi-stage stimulation that was seemingly fast and efficient in high pressure environment loses its appeal in sub-hydrostatic pressure wells. The time spent between each stimulation stage to the onset of well flowback becomes long and detrimental to the recovery of the well. The fracturing fluid lost to the formation can negatively alter the relative permeability of gas in the reservoir and the longer the time spent to recover the fluids the damage tends to get irreversible. Quick and efficient clean-up of fracturing fluid is indispensable to maintain a well's productivity in tight, low pressure gas reservoirs. A new generation of multi-stage completion systems is discussed in this paper. These multiple stage tools are operated by a single ball that opens several of the treating sleeves in one run thus allowing a large section of the reservoir to be treated simultaneously. The stimulation fluid placement is enhanced by pumping through limited entry ports of the stimulation sleeves at optimum injection rates supported by modern particulate diverting agents, and energized fluids. The operation time between the first stimulation (acid) stage hitting the formation to the well being flowed back can be cut down to a matter of few hours from an otherwise operation of a few days. The results from this step change in completion and stimulation design have been spectacular providing several folds of productivity improvement. This application provides a fundamentally sound solution for treating low pressure, tight reservoirs.
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