When your mature environment is in decline, trust us to see it differently. Brownfields

Transcription

1 When your mature environment is in decline, trust us to see it differently. Brownfields

2 Photograph taken in The Cave Without a Name, Boerne, Texas.

3 WHITE PAPER Brownfields Schlumberger is an oilfield services company supplying technology, project management, and information solutions to the E&P industry. Executive summary Typically in oil and gas production, the keenest interest and greatest investment is focused on the early life of a reservoir its productive heyday. But times are changing. These days, brownfields defined as mature fields in a state of declining production or reaching the end of their productive life are regarded as potential fountains of youth. In an industry climate marked by growing demand, ever-greater importance is placed on enhancing and prolonging an asset's productive maturity, maximizing its declining productivity, and postponing its demise. Schlumberger has long recognized the need for cradle-to-grave technology; now, nearly 60% of the company's well services business is channeled toward rejuvenating brownfields. Author Usman Ahmed Theme manager, Brownfields Contributors to this paper Donna Garbutt, Lorne Simmons, Martin Isaacs, Leo Burdylo, Carl Trowell, and Karen Glaser Schlumberger

4 Brownfields Brownfields generally are more than 30 years old and account for 67 72% of world production. One look at the World Energy Organization Basin Exhaustion S-Curve brings the task of the exploration and production (E&P) industry into focus. Brownfields, defined as mature fields in a state of declining production or reaching the end of their productive lives, contain resources that are needed by producing countries and the world economy. These brownfields generally are more than 30 years old and account for 67 72% of world production. When compared with other fields deepwater and greenfield brownfields represent the most significant capacity to provide future production. Headliner deepwater developments account for only about 8% of global production, and greenfields (those fields under development, or producing and perceived as having a high percentage of reserves still in the ground) account for another 20 25%. While brownfields hold the majority of oil resources, the recovery factor is currently only about 35 37%. This must be increased dramatically if we are to achieve the 1.7% (11 million barrels of oil per day) growth in output needed to satisfy predicted demand between now and So why are we not seeing more recovered reserves from brownfields? The reasons are complex, as much driven by resource and portfolio decisions as by geological factors. Many mature fields are being operated using technology put in place when the field was originally developed. Technologies routinely applied in new field developments are being ignored in brownfields, and many of these fields are underperforming and require engineering and operational attention. While increasing asset value through improved reservoir performance in such fields has been desired for decades, productivity and recovery results have been difficult and even impossible to attain because critical tools and technologies were either not made available or inadequate. Ineffective or problematic initial completions Unstimulated horizons Low fracture conductivity Short fracture length High skin, or damage Gradual formation damage during production Scale and fines Workover frequency Well age Well underperformance Outdated technology Advanced stimulation technology New completion techniques Well age Fig. 1. Potential causes of underperformance in previously stimulated wells. The GTI restimulation project team established a classification framework to help diagnose problems in hydraulically fractured wells that perform below operator expectations. At the highest level, there are three broad categories: ineffective or problematic initial completions, gradual production damage, and advances in technology or evolving techniques compared with past practices. 2 White Paper

5 World Production (%) Fig. 2. Current world production Brownfields Deepwater fields Greenfields Many mature fields are being operated using technology put in place when the field was originally developed. Shouldering responsibility for brownfield development Schlumberger experience has shown that improving recovery from mature fields requires an application of practical and focused engineering coupled with the introduction of new technology. Most importantly, it requires specialization. Schlumberger made a commitment 25 years ago to actively address brownfield challenges particularly in the area of risk and cost reduction. That commitment remains true today. For 75 years, our mission has been to tackle projects in any area of the world. The required collaboration between client and operator has brought about an expertise that translates well to brownfields and a unique flexibility in technology and in product development. Fit-for-purpose technologies already developed or under development offer ways to reach production goals and take efficiency in brownfields to new levels. Current efforts to improve recovery rates involve better reservoir knowledge for understanding bypassed pay in existing fields and unrecovered oil in produced zones real-time data delivery and decision systems improved access to reservoirs tailored technology, process offerings, and expertise full partnership capability and project management. Short-term production goals are often achieved at the cost of high decline rates. Over the long term, a sustainable production plateau is sought. The greatest technology challenge is preparing for and enabling management of decline in the short term while increasing recovery factors in the longer term. Managing production decline The maturing fields in North America have taught us that unlimited capital spending cannot reverse decline. While technology without expert direction and careful selection should not be considered a panacea, the technologies needed to slow, halt, or reverse production decline fall into these categories: reevaluation of reservoir remediation of wellbores and facilities efficiently targeting bypassed or undeveloped reserves production optimization, especially completion and lift strategies fluid management in general, including water management. White Paper 3

6 Brownfields Schlumberger made a commitment 25 years ago to actively address brownfield challenges particularly in the area of risk and cost reduction. That commitment remains true today. Reevaluation understanding the big picture A key part of field reevaluation is to understand the current state of production. A new, rigorous evaluation to create a comprehensive reservoir model is required and is accomplished by reevaluating existing data and gathering new data to recharacterize the reservoir. Some fields are so old that formation data are unavailable or sparse. In fields where formation data are scant, identifying the remaining pay can be accomplished using new formation evaluation techniques to better understand the mechanisms at work in the reservoir. Advances in resistivity logging technology have improved cased hole formation evaluation and have also demonstrated remarkable results in detecting fluid behavior in declining reservoirs. A cased hole formation test tool with success rates in excess of 95% is being used to obtain multiple samples in a single descent and to identify bypassed resources, such as oil swept to another part of the reservoir as a result of waterflood. Production logging technology is used to analyze current well and reservoir production and identify opportunities for improvement. At the scale of the field and the well, knowledge of individual performance can help optimize production and manage decline. Looking to the future, today s greenfields are benefiting from real-time information, which is having a significant impact on all technical areas and is extending the peak of production. Customized intelligent systems are helping optimize productivity for tomorrow s brownfields. Technology enhancements enable correct on-the-spot decisions and solutions involving integrated cross-disciplinary services. Today s remote monitoring devices and information systems offer the option of understanding what is taking place in the reservoir and the ability to take corrective action in real time. Remediation infill drilling and recompletion Reservoir management provides a better knowledge of fluid distribution in the reservoir. This in turn means that highly effective well profiles can be planned for infill drilling. Advanced imaging techniques allow the operator to select the best locations for infill drilling to optimize well placement and to apply new cost-effective drilling methods. Better steerability, improved dogleg capability, and slimmer tools have been developed to drill technically difficult wells, e.g., complex trajectories to intersect as many target zones as possible or to reach one sweet spot. Kd Kf Fig. 3. The frac-pack bypasses near-wellbore damage (Kd) and creates effective communication between the undamaged formation (Kf) and the wellbore. 4 White Paper

7 Specially designed seismic apparatuses are being incorporated into new drilling technology to allow better formation imaging while drilling. The logging suite delivers crucial real-time data for evaluating the positioning of drilling strings and modifying the well path as needed. Particularly useful in mature reservoirs in which pressure has been a longstanding challenge is a new perforating system that controls an optimum dynamic underbalance reservoir pressure. New techniques minimize disruption of the cementsandface hydraulic bond and create optimum perforation shape and length. Production breakthroughs in fluids and fracturing Innovative technologies smart matrix and fracturing stimulation fluids as well as next-generation deployment methods like highly versatile coiled tubing (CT) fracturing units are being applied not only to revive hydrocarbon production in mature fields, but also to develop greenfields with a view to efficient, longer-term production management. One of the key benefits of CT is that it fits inside the completion string, so precise deployment of fracturing tools and fluids is possible at lower cost. Selective treatments and smart placements are becoming the techniques of choice. They are maximizing acid coverage specific to each layer of a formation, increasing utilization of the fluid for greater returns, often without mechanical intervention. One smart fluid is capable of plugging water zones while stimulating oil zones. Use of various types of fracturing fluid has resulted in better control over fracture geometry by altering viscosity without compromising the ability to transport proppant. This allows fracturing treatments to be executed in producing zones close to water tables and with minimum stress differential. Water management boosting watereddown profits In brownfields, water handling treatment, transport, and disposal of recovered water; sale of potable water; or reinjection programs continues to be addressed with great care. With the average worldwide water cut estimated at 75% and increasing, the issue of separating fluids at the Fig. 4. Nonpolymer viscoelastic fracturing fluid. surface will be with the industry for the foreseeable future. Dealing with water is a costly fact of life in most mature fields, with the average industry operating expense at USD 0.50 per barrel of produced water. Pumping units and surface operations originally designed to handle oil and minimal water are now producing primarily water and only traces of oil. For example, California oilfields now operate on the average at a water/oil ratio of 7:1. Disposal legislation regarding produced water is on the increase worldwide. Why is water such an overwhelming factor in brownfields? Incompatible completions as a result of production changes are one reason for the problem. Increased water cut is related to reduced recovery and surface facility bottlenecks. Also, historically, there has been a fragmented approach to water handling. The greatest technology challenge is preparing for and enabling management of decline in the short term while increasing recovery factors in the longer term. White Paper 5

8 Brownfields Remaining zones of bypassed oil often require complex well trajectories that intersect as many target zones as possible. The focus of future technology and process efforts will involve downhole separation and disposal of water to reduce surface handling and to allow surface facilities to process more oil prevention of water entering the wellbore through the use of chemical or biological agents integrated evaluation and engineering processes to identify the type and location of water breakthrough improved reservoir energy management, including optimized water injection schemes, water front prediction, and improved sweep efficiency. Cost-effective solutions for declining margins The most recent developments in brownfield technology and software, coupled with project management expertise, help to mitigate the risks inherent in mature field portfolio additions. In the mature field environment, integrating technology is critical to success. The challenges of declining production and a mature asset can be met by altering the way reservoirs are developed and managed from discovery through depletion and abandonment total field life cycle management. From the first stimulation performed in 1932, it was anticipated that production enhancement technology would have to evolve to align with future operator needs. Now, the need for operators to become more cost competitive is forging a stronger bond between operator and service provider. Increasingly, operators are turning to service companies to provide an integrated approach to rehabilitating brownfields, bringing focused engineering, technology, and management techniques to fields that have often been neglected. This integrated project management (IPM) approach starts with a total reevaluation of the field in order to understand the fluid and pressure distribution of the reservoir; from this, an efficient and executable redevelopment plan is derived and carried out. The results can be significant when the right technology and processes are applied. Our efforts to rehabilitate brown fields are commonly undertaken through a long-term alliance or partnership that involves working with asset owners to achieve production or reserve goals. As an integrated service company with a specialist project management group, we are able to apply field management, well construction and intervention, and project and risk management skills to rehabilitate brownfields in an integrated manner that brings together fit-for-purpose technology solutions. Each rehabilitation project is unique and tailored to match the objectives of the project and the goals of the project owner. When properly managed, a rehabilitation project should be guided by a clearly defined scope of work, a detailed project execution plan for handling all contingencies, and a planned ability to manage change. Often the first action in identifying which fields have the potential for major rehabilitation is to undertake a field optimization study (FOS) that will examine the total field production operations with the objective of improving profitability through identifying opportunities for increased production, decreased costs, and improved water management strategies. From the FOS, an overall field redevelopment plan can be engineered to implement the changes necessary to revitalize the field. Field management processes can be optimized by real-time integration of new data into the field redevelopment plan and using simulation and economics tools to guide decision making. Coaxing more oil from the reservoir Because today s greenfields are tomorrow s brownfields, the task of the service company is to develop and cost-effectively deliver better permeability data better prediction of likely fracture geometry better understanding of the reservoir better integration of job planning, execution, and follow-up more productive fields better financial returns. 6 White Paper

9 Only a solid commitment to research and development and innovative thinking can deliver reservoir-focused applications and effect positive change in efficient delivery of well services to drive down lifting costs and coax more oil from the reservoir. Enabling old fields to bounce back Technology to economically restore production in depleted reservoirs is being developed to address the complex issue of increasing production without adversely affecting the decline curve. During the past few years, a number of Schlumberger technologies particularly applicable to further development of brownfields Conventional fracture stimulation Inadequate fracture length Stage 4 3 have emerged. Some of these technologies, addressing all four areas of reservoir production enhancement, include ABC * Analysis Behind Casing services Memory PS Platform * production services PowerDrive * rotary steerable drilling systems seismicvision * logging while drilling tool PURE * Perforating for Ultimate Reservoir Exploitation system PowerCLEAN * integrated system for effective wellbore fill removal OilSEEKER * acid diverter VDA * Viscoelastic Diverting Acid Stage Selective fracture stimulation Optimal fracture length Innovative technologies... are being applied not only to revive hydrocarbon production in mature fields, but also to develop greenfields with a view to efficient, longer-term production management. Marginal pay zone 5 Additional reserves Insufficient interval coverage Complete interval coverage Bypassed pay zone Additional reserves Perforations Wellbore Fracture Casing Fig. 5. Conventional and selective stimulations. Fracturing several zones grouped in large intervals, or stages, is a widely used technique. However, fluid diversion and proppant placement are problematic in discontinuous and heterogeneous formations. Conventional treatments, like this four-stage example, maximize fracture height, often at the expense of fracture length and complete interval coverage (left). Some zones remain untreated or may not be stimulated adequately; others are bypassed intentionally to ensure effective treatment of more permeable zones. Selective isolation and stimulation with coiled tubing, in this case nine stages, overcome these limitations, allowing engineers to design optimal fractures for each pay zone of a productive interval (right). White Paper 7

10 Brownfields The average worldwide water cut estimated is at 75%. ClearFRAC * surfactants FloVIEW * holdup measurement tool GHOST * Gas Holdup Optical Sensor Tool RSTPro * Reservoir Saturation Tool for PS Platform string. Formation evaluation ABC services allow complete formation evaluation through casing. Not only has this resistivity logging technology enabled cased hole formation MD 1 : 120 ft Gamma Ray 0 (gapi) 50 Compressional Coherence 0 1 Shear Coherence 0 1 Standard processing 40 (µs/ft) 220 evaluation to gain in efficiency, it has also revealed remarkable results in detecting fluid behavior in declining reservoirs. The Memory PS Platform service, along with the FloView, GHOST, and RSTPro tools, is making a difference in the area of production logging. Memory PS platform measurements clearly identify entry points of oil and water into the wellbore with the same accuracy and quality as real-time configurations in situations that preclude surface readout operation. Casing-optimized processing 40 (µs/ft) 220 X,X50 X,X60 X,X70 X,X80 X,X90 X,X00 X,X10 Fig. 6. Tools centered in the casing, low-frequency firing, and optimized transmitter-receiver tool spacing give ABC casing-optimized processing (right) better coherence and continuity than standard processing (left). 8 White Paper

11 Drilling and perforating The family of fully rotational PowerDrive systems allows optimization of drilling from kickoff. Kicking off from vertical in an to in. hole to extended reach drilling to in. or even in. hole is now possible. Drillstring sticking is reduced because there are no stationary components contacting the casing, whipstock, or borehole. Penetration rates are also improved, because there are no stationary components to create friction during operation. Continuously updating the bit on the seismic maps with seismicvision logging while drilling capabilities helps in navigation In the mature field environment, integrating technology is critical to success. selecting casing and coring points target depth prediction reducing sidetracks and pilot holes. Acquired interval velocities provide the data necessary for managing pore pressure while drilling and optimizing mud weight. Careful control of reservoir dynamics is critical to the success of the perforated completion. Previous neglected variations in wellbore parameters have a profound effect on the performance of the completion. By basing job design on the properties of the reservoir, wellbore, and gunstring, the novel PURE technique consistently minimizes or eliminates perforation damage to maximize productivity. The wellbore in many mature fields can become clogged by sand, silt (proppants), and other particles; keeping the perforation holes clear is an important step to improving production. The PowerCLEAN solution uses a CT system to remove clutter in many challenging environments. Stimulation and water control OilSEEKER acid diverter for sandstones and carbonates selectively plugs zones with high water saturation. The acid enters the zones with high oil saturation. Use of this smart diverter makes matrix stimulation easier and safer without the nitrogen used in foaming operations. Fig. 7. Depth control is paramount in fracturing through CT. VDA fluid is based on unique Schlumberger viscoelastic surfactant technology. Because it is polymer-free and self-diverting, the fluid can prevent formation damage while providing total zonal coverage. The ClearFRAC polymer-free fracturing fluid system was developed to provide maximum fracture conductivity as a result of minimum damage under a range of conditions. Designed to operate with significantly lower friction pressure while pumping, this fluid has low hydraulic horsepower requirements to reduce equipment demands. By maintaining a constant viscosity, the ClearFRAC fluid offers a means to predict and control fracture geometry. In brownfields, corrective actions with the selection and application of intelligent technologies and advanced methods in conjunction with reliable, verified data ultimately define project success, enabling fields that suffer from production falloff to make a comeback. White Paper 9

12 Technology is key. Today s brownfields have accounted for the majority of world production, yet hold even greater potential for additional recovery. The way we see it, these mature, declining fields offer the greatest promise for the future. Growing demand for energy and innovative recovery techniques means it pays to take a second look at these potential wins. Schlumberger Oilfield Services (OFS) brings you advanced tools and expertise to better understand the environment. Advanced simulation software Cementing technology Drilling services Expert services Formation evaluation tools Information services IPM Multilateral completions Perforating services Stimulation technology Schlumberger leads the way. To learn more about brownfields, visit OF_04_016_0 Schlumberger January 2004 *Mark of Schlumberger Produced by Oilfield Marketing Communications, Houston.