Session Chairs: Ahmed Ouenes, SIGMA3; Dipika Kataky, RPS Energy
This session focuses on the need to examine unconventional reservoirs and the use of hydraulic fracturing technology through a multidisciplinary approach. The successful selection, design, and execution of a fracturing treatment require a good understanding of multiple rock properties along the wellbore and its surroundings.
This understanding requires the simultaneous use of petrophysics, geology, geochemistry, geophysics, and geomechanics in an integrated fashion to identify the optimal fracturing locations. The session will attempt to answer practical questions related to the selection of fracturing sweet spots, the monitoring of the fracturing execution with microseismic and the possible actions that could be taken during and after the fracturing to enhance well productivity.
The session will also attempt to describe and discuss specific workflows that illustrate the multidisciplinary integration when selecting fracturing sweet spots.
Session Chairs: Leopoldo Sierra, Halliburton; Pedro Saldungaray, Carbo Ceramics
Hydraulic fracturing is a critical component in the successful development of tight and shale gas reservoirs. The primary goal is to contact as much rock as possible with a fracture or a fracture network of appropriate conductivity to enable commercial recovery of a large volume of reserves per well. This objective is typically accomplished by drilling horizontal wells and placing multiple transverse fractures along the lateral.
On one side the completion must be designed to address the reservoir needs by engineering the wellbore placement in the reservoir, fracture spacing, geometry, and conductivity. On the other side, given the operational intensity of this type of completions, operational efficiency plays a major role in the economics and viability of unconventional gas developments and cannot be overlooked. These two aspects are not simple to be optimized simultaneously and often times are at odds.
This session will explore the conflicts as well as compromises and hopefully synergies asset teams face when integrating the available completion hardware and isolation techniques with reservoir considerations when defining field development plans and well designs for unconventional gas.
Session Chairs: Dipika Kataky, RPS Energy; Zillur Rahim, Saudi Aramco
Unconventional gas does not flow easily. These reservoirs are usually heterogeneous, complex, and often developed in geologic systems that are poorly understood and arguably more difficult to drill and develop. The first unconventional gas projects were developed with fracture-stimulated vertical wells. The next phase was to drill horizontal and multilateral wells to maximise reservoir contact. Recent technological developments like pad drilling are changing the dynamics of exploration and production in the unconventional resources. Presently more than 20 wells can be drilled from a single pad opening up large portions of tight formations from a single surface location. The single horizontal wells are completed with multi-stage fracture treatments, ensuring high reservoir contact area needed to enhance gas rate and for commercial production. With the use of geomechanics, wells are routinely drilled in the direction of minimum horizontal in-situ stress to enable creation of multiple independent hydraulic fractures.
Currently 62% of the wells are horizontal and expected to double in next five years worldwide. This is because these wells, along with induced multi-stage fractures, produce at commercial rates, recover reserves sooner, and also contribute to higher ultimate recovery. Reservoir properties strongly affect the drilling of horizontal wells. Reservoirs need to be thoroughly studied and understood, and geomechanical modelling needs to be conducted to determine appropriate mud-weight window to ensure wellbore stability, compute accurate in-situ stress profile of the region and for a particular well to facilitate fracture design. The wells need to be drilled with accurate landing point and be placed within the target zone. Studies suggest that as more unconventional gas resources are explored and developed, the average permeability of the producing reservoirs will continue to decrease, requiring the industry to apply new drilling technologies and intelligent practices that enable wells to produce at economic rates. One of the key things which will make unconventional gas play work is novel drilling technology.
Technology drives development. It is important to find more ways to optimise well planning. There is potential for a quantum leap in drilling and completion efficiency. Application and use of novel technology is required to minimise formation damage, breakdown or breakouts, and understand rock-fluid interaction. Drilling direction, azimuth, techniques, mud weight, use of centralisers for proper cement placement, appropriate choice of open hole or cased completion, use of correct stimulation technology are all vital for the successful development and exploitation of unconventional gas reservoirs. Finally, best practices can always be obtained from field experiences and lessons learnt.
Session Chairs: Nihat Gurmen, Schlumberger; Zillur Rahim, Saudi Aramco
The hydraulic fracturing is a very interesting and complex engineering problem. The main objective is to enhance and sustain well productivity and increase ultimate recovery at a faster pace. The multidisciplinary nature of hydraulic fracturing spans the knowledge domains of geology, reservoir engineering, rock mechanics, fluid mechanics and chemistry, completion, and field operations.
The reservoir engineering part is very crucial and provides the requirements of a hydraulic fracture design in terms of geometry and fracture conductivity to achieve a desired production target. This target is typically part of a bigger reservoir management and field development strategy. The other knowledge domains provide the necessary tools and constraints to design a treatment meeting reservoir engineering requirements. The hydraulic fracture design formulation for conventional wells with typical shale-sand-shale sequences have been in use for decades now. They still form the foundation of fracture models today.
However, the advent of unconventional gas resources and available computational power and efficiency brought in many new ideas to improve modelling of laminated thin zones, multi-stage fracture treatments along long horizontal wellbores, and interaction between hydraulic and natural fractures by incorporating core and geomechanical concepts into fracturing design and modelling. These advances have been matched with improvements in fluids and proppants as well, leading to robust high-temperature, salt-water tolerant, and non-damaging fluids, and novel proppant shapes, sizes, and materials.
This session will focus on fracturing design and modelling concepts encompassing core modelling as well as materials that improve the overall process.
Session Chairs: Mansour Shaheen, Baker Hughes; Pedro Saldungaray, Carbo Ceramics
The foundations of shale-specific well completions, fracturing and production operations have been evolving for more than three decades and in fact shale gas production dates back almost one hundred ninety years. During the last decade of gas shale developments, the projected recovery of gas-in-place has increased from a mere 2% to estimates approaching 50%. This remarkable achievement has been built through the development and adaptation of technologies to fit shale gas developments particular conditions. Adapting technologies, such as multi-stage fracturing of horizontal wells, slickwater fluids with minimum viscosity and simultaneous fracturing, have contributed to enhance the access to reserves. From localised single fractures with limited formation contact used in the past, today the industry is capable of placing intricate fracture systems connecting and opening natural fractures.
These technologies have made possible the development of enormous gas reserves that were completely inaccessible only a few years ago by transforming filed development economics. Current and next generation technologies promise even more energy availability with advances in hybrid fracturing, fracture complexity, new fluids and proppants, fracture flow stability, and methods of re-cycling water used in fracturing.
The interlinking of Geosciences, Well Engineering, and Operations and Information Technology into best practices will continue to yield best results, while at the same time encourage companies to explore and invest in research for technologies and processes in the challenging arena of shale gas. Nowadays shale gas extraction looks much more like a manufacturing process in comparison to the development of a conventional natural resource. Optimising the process is the challenge and continuous development of best practices will take us there.
Session Chairs: Fahad Al-Alawi, Abu Dhabi National Oil Company; Leopoldo Sierra, Halliburton
Unconventional gas exploration and development typically requires more wells and hydraulic fracturing than conventional wells. Highly efficient practices are necessary to keep exploration and development costs low and improve field economics by overcoming effectively the normal logistical changes, lack of equipment or supply chain management challenges.
Highly engineered equipment, water, proppant or chemicals and processes that minimise unnecessary movement and excess equipment and fluids will reduce the NPT and improve the efficiency of the entire process. This will also minimise the environmental impact through reduced footprint and by water handling minimisation.
This session will review and discuss the normal logistical and supply channel management challenges the industry is facing to explore or develop unconventional gas.
Session Chairs: Ahmed Ouenes, SIGMA3; Robert Clark, BP
High quality pre and post frac surveillance provides significant opportunities to enhance the execution of an individual fracture treatment or an entire fracturing campaign. Real-time data can be highly useful in evaluating fracturing operations. For example, permanent downhole gauges provide actual bottom hole treating pressures, which in turn, can detect imminent screenout conditions earlier and reduce the chances of damaging a well.
In a pre-frac application, a small water injection treatment can be analysed, often referred to as "After Closure Analysis". The reservoir is static prior to this injection so a limited volume of fluid perturbs the reservoir very little. This is relatively uncomplicated to analyse compared to typical post frac flow and pressure build up surveys. A short term PBU in a tight gas well usually delivers only a fractured well signature as it takes months to years to detect pseudo-radial flow. On the other hand, an ACA test has only minimally disturbed the system and it is not unusual to detect pseudo radial flow. This inexpensive injection test can provide fracture gradient, kh, and P*.
Microseismic technology is at an advanced stage of development in North America but is not widely conducted elsewhere as yet. This technology enables analysis of fracture geometry, height growth, fracture extension, and regional stress direction. This information assists in field development decision planning for well spacing and well azimuth in horizontal drilling.
This technology enables operators to monitor fracture growth laterally and vertically during active fracture operations. The most common system is to place geophones in a monitoring well and gather seismic data while fracturing operations are on-going in the target well. Finding suitable observation wells presents major challenges outside of North America. Post-fracturing flowback is critical to evaluate the actual success of the fracturing effort and to clean out proppant and fracturing fluid. It also provides a chance to obtain reservoir fluid chemistry and PVT samples.
Session Chairs: Fahad Al-Alawi, Abu Dhabi National Oil Company; Robert Clark, BP
Case studies are an invaluable record of the technical practices of professional engineers. While case studies cannot provide specific guidance for the management, they are an instrumental record of technical, theoretical, and operational interactions which may help to frame questions for more rigorous decision making.
This session is intended to focus on integrated case studies about unconventional gas fracturing stimulations which have been applied in the Middle East. These case studies will demonstrate best practices and lessons learnt for unconventional stimulations as well as pose challenges and opportunities for industry to notice and tackle.