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Unconventional Gas Fracturing: Leveraging Experience from Success
and Failure

5 – 7 November 2012

Dubai, UAE | Amwaj Rotana - Jumeirah Beach Residence

Technical Agenda

Session 1- Reservoir Characterization

The aim of the session is to create a common understanding on unique characteristics of unconventional reservoirs as related to designing hydraulic fracturing stages. The focus is how the data from various disciplines of reservoir characterization: petrophysics, geology, geochemistry, geophysics, and geomechanics, is integrated to design a fracturing program for a given well. Critical questions will be raised and discussed to enhance understanding on what models do we currently use in petrophysics and how they should be applied to unconventional reservoirs, how geosciences help in identifying sweetspots for fractures initiations, what makes shale gas different from one basin to another, which parameters control the decision on locations and design of staged fractures. The session will include technical papers and discussion on understanding how conventional reservoir characterization should be avoided when dealing with unconventional reservoirs and the new tools and techniques being applied to maximize production from these challenging reservoirs.

Session 2 - [Panel Session]: Frac Design

This session is designed to include joint presentations by service companies.

Unconventional gas will require detailed attention to frac design and not only from the point of how much proppant should be placed with each frac; although, this is the ultimate goal of the frac process. One should look at the design as a process, from gathering prejob data from, for instance from geology, petrophysical interpetations of logs and cores, well completion and others. It is important in the pre-job phase to build a reservoir model in the fracturing simulator that uses all data available.

The pre-frac diagnostics injection tests are a critical part of the frac design as the aquired data can be used in the fracturing model to validate reservoir but also fluid characteristics. Multi-rate testing can give valuable information about wellbore connectivity to the fracture and may result in some remedial pumping or perforating in order to ensure successful placement of the frac treatment.

Unconventional reservoirs require a special approach to fluid design as well as the actual pumping schedules, and modelling the fractures with simulators is critical. One will require certain fracture geometry and conductivity to ensure the zone can be produced economically.

This panel session will focus on these frac design issues. Service companies are invited to make a short presentation covering some of the above aspects on Frac Design (case histories from ME area are very welcome). The presentations will be followed by a panel discussion all participants of the workshop.

Session 3 A- Completion Design (Reservoir Perspective)

Unconventional gas reservoirs cannot be produced with conventional methodologies. Maximizing return in these environments needs the best completion design for the life of the well and long-term production of the reservoir. Well deviation, drilling direction, multi-stage hardware, hydraulic fracturing design, and execution are all major contributors to the long-term success of a project. Therefore, all these factors need to be optimized in an integrated process that takes the interactions between them into account and with hydraulic fracturing in mind from the start.

This session will present the latest developments that have occurred in the region in utilizing multistage fracturing technologies. It will address the reservoir specifics needed for successful treatment of unconventional wells. These specifics will include well placement strategies, use of multi-well pads, lateral length and azimuth choices, individual stage lengths and number of stages, geometric vs. reservoir-centric staging options, hardware selection, slot cutting vs. perforation to minimize tortuosity, hence, fracturing and breakdown pressures.

Session 3 B - Completion Design (Hardware Perspective)

Development of tight gas resources has evolved to increasingly complex and lower permeability reservoirs. In this setting, conventional well completions have been pushed to the limit in their ability to deliver economically viable wells. In order to respond to this challenge and improve economics, the industry has turned to horizontal wells with multiple hydraulic fractures. The many completion tools and placement techniques developed enable maximized production from increased reservoir contact in a cost effective manner by optimizing the utilization of both the personnel and equipment needed to perform the work. This session presents the latest developments that have been made available to the industry in multistage fracturing technologies.

Session 4 - Fracturing Materials

Hydraulic fracturing involves the injection of fluids into the formation at a rate and pressure above the fracture pressure of the reservoir in order to create a fracture within the rock itself. The resulting space is filled with proppant which:

  • Improves the productivity and ultimate recovery of the well
  • Creates a high permeability pathway from the productive formation to the well
  • Improves EUR (Estimated Ultimate Recovery)

At first glance, the process seems quite simple using four main constituents: water, proppant, additives, and other fluids. However, the fracturing process and nature of the formation requires detailed design of the fracture project and necessitates close scrutiny when selecting the type and quantity of fracturing materials. At closer inspection, a wide variety of fracturing materials may be needed to successfully fracture the formation, achieve good initial production, and support estimated ultimate recovery.  Some of those materials include:

  • Gelling agents
  • Friction reducers
  • Cross linker control
  • PH adjusting agents
  • Scale inhibitors
  • Bactericide
  • Resin coated sand
  • Acidizing chemicals
  • Clay control
  • Activators
  • Ceramic/bauxite proppant

This session of the ATW will focus on educating attendees on the types of materials used and their performance capabilities. It will also provide excellent knowledge transfer between presenters and attendees on innovative materials technologies and how they have been applied in the practice of hydraulic fracturing for unconventional gas.

Session 5 - Operation Challenges

Most of the tight gas resources are located in remote, deep and high pressure, high temperature environments that bring unique operational challenges to hydraulic fracturing treatments. Deep and high pressure environments demand the use of high density fracturing fluids or the use of 20K fracturing equipment that are not readily available in all the areas. At the same time, the water, chemicals, proppant, or equipment need to be planned well in advance. In almost all the cases these challenges limit the normal flexibility that operator and service companies need to have to optimize the stimulation process.

The Operational Challenges session will cover the typical planning necessary to conduct actual fracturing operations. Particular attention will be paid to specific conditions in the Middle East where the climate and lack of primary infrastructure can pose additional logistical problems. Typically desert and road conditions require different trucking specifications from many other locations.

Proper trip planning is essential, and personnel need training in survival, both in the desert and offshore operations. Fracturing equipment needs to be suitable for the hot and often dusty climate, and fluid handling has to be planned carefully. On the positive side, low population density make layout and noise less of an issue in many Middle Eastern locations. Water availability and usage may be of a premium, and could be discussed in this session. The heat and UV can cause storage problems for chemicals and their packaging, as well as additional hazards to the crews setting up and performing the operations, and these need to be addressed too. Fluid temperatures are often elevated, and this needs additional testing and potentially chemical adjustments.

In addition to the climate, many fields in the region contain H2S and require special steels to be used, and some fields are prone to the production of scales and asphaltenes which need to be taken into account.

Case histories on the challenges faced in the Middle East are invited for presentation in this session as well.

Session 7 - Post Frac Flowback and Cleanup , Well Testing, Production Diagnostics, and Microseismic

Immediately after the fracturing treatment, a well is flowed back for cleanup. Sometimes 24 hour shutin is practiced prior to flow back if resin coated proppants (RCP) are used which cures within that time. Fracturing operation is not completely successful unless the fluids pumped are thoroughly broken down and cleaned up and the proppant pack restores it conductivity. A well can lose substantial flow potential due to impairment of proppant conductivity from the residual gel and fracture face skin. Use of appropriate polymer breaking agents in optimal volume pumped toward the end of the job, and even later, is therefore critical and essential for improved productivity.

The analysis of a successful treatment will require reservoir properties, pre and post frac flow rates, and effective fracture characteristics. Well testing collects many of these data with much precision and is therefore an essential element to gauge the effectiveness of a treatment and associated benefits. The production history data must be analyzed and compared to the post-treatment long-term stabilized rate. In terms of fracture treatment, the most important measure of success is to match, as closely as possible, the fracture dimensions and proppant conductivity computed from well testing and production data analysis to the numbers calculated from fracture simulators using actual pump data and geomechanics. In terms of well productivity, the rate should be calculated using the properties measured by open hole logs and confirmed by well testing to check if actual well performance matches operator’s expectation and is consistent with reservoir and fracture properties.

Microseismic is a helpful tool to diagnose fracture geometry and growth pattern, stress directions, and thereby help in developing a field with proper placement and spacing of wells and optimizing hydraulic fracture treatments. Microseismic requires careful observation and collection of data while a fracturing treatment is ongoing. Many different ways to collect data are available–from the surface or buried geophone arrays or from nearby observation wells. For the surface arrays, the sanitizing the data from surrounding noise is essential. The microseismic technology is mainly used in the shale so as to understand the stimulated reservoir volume and the extent of induced fracture coverage.

Modeling work and case histories on pre and post frac well flowback, cleanup, productivity increase, well testing are invited for presentation and discussion in this session. Information on different types of fracture fluids and breaker systems used and the associated benefits will be very helpful to the session attendees.

Session 8 - Innovative Technologies

Current fracing technologies rely heavily on the availability of fresh water which could be a major problem in many regions of the world including the Middle East. This session will present innovative technologies to reduce the reliance on fresh water by using foamed fluids that will incorporate CO2 and N2 gases. Because the use of gases could pose safety issues, the other alternative technologies considered for reducing the use of fresh water is the use of sea water, brackish water, and brine. Successful field examples using these alternatives water sources are described in this session.

Among other innovative technologies discussed in this session are new geophysical approaches used to map and interpret in 3D the microseismic events resulting from multiple frac stages. These technologies are used to improve the modeling and interpretation of the induced fractures and the resulting SRV, thus providing a better estimate of the production rates and reserves.