Injection Wells for Liquid-Waste Disposal. Long-term reliability and environmental protection

Transcription

1 Injection Wells for Liquid-Waste Disposal Long-term reliability and environmental protection

2 ACHIEVE MULTIPLE GOALS FOR LIQUID-WASTE DISPOSAL INJECTION WELLS Expertly located, designed, constructed, and operated injection well systems permanently remove liquid wastes from the biosphere, often at a significantly lower cost than other disposal options. Protect the environment Successful protection of the environment by a liquid-waste injection well system depends on close collaboration between the customer, regulators, and experts in the design and construction of injection wells. Permanently preventing any upward migration of injection waste into overlying aquifers sources of drinking water must begin with an assessment comprising an appropriate and efficient aquifer and subsurface characterization program, data management, and verification of local conditions. The assessment must also identify low-permeability confining strata and assess risks related to water flow, adverse geochemical processes, induced fracturing, and induced seismicity. Streamline regulatory approval process Efficient management of the permitting process for the construction and operation of injection well systems reduces costs and avoids project delays. Keeping projects on schedule and controlling costs requires expertise and experience in subsurface characterization, injection well system design, permitting agency workflows, well construction and testing, and operation and maintenance. Achieve target disposal capacity cost effectively Designing injection wells to accept target liquid-waste flows at the lowest possible injection pressure maximizes injectivity (defined as the ratio between the injection rate and pressure increase) and significantly reduces costs by meeting the required disposal capacity with fewer wells. A detailed geological characterization program is used to locate the most favorable formations for injection, and identifying the most efficient completion and stimulation processes optimizes well design. Drinking water source Maintain performance throughout well life Maintaining disposal capacity throughout the planned operational life of an injection well system is critical. To prevent well and formation clogging by chemical (mineral) precipitation, biological growth, suspended solids, or dispersion of clays, many strategies can be implemented. The first step is to conduct a compatibility analysis, which may involve geochemical modeling and laboratory testing with the anticipated composition of the liquid waste. Next, injection wells are designed to minimize their vulnerability to clogging and to facilitate well rehabilitation should clogging occur. Last, procedures are put in place to manage the effects of changes in liquid-waste composition. Several thousand feet Treated municipal wastewater Confining formation Confining formation Hazardous and nonhazardous liquid waste Confining formation

3 MAXIMIZE RESULTS VIA AN INTEGRATED PORTFOLIO OF SERVICES Underground injection reduces potential human exposure to liquid wastes by removing them from the environment. Injection wells are a reliable, economical, and environmentally sound solution for the disposal of these wastes. Although deep injection has an outstanding safety record, its skilled execution is essential. Schlumberger Water Services integrates expertise and technology to provide a complete set of services for long-term reliability, economy, and environmental protection. Liquid wastes disposed in deep injection wells include hazardous and nonhazardous industrial wastes, brines, and municipal wastewater. Complete Suite of Services Feasibility studies Permitting Injection well system design Construction Construction supervision Formation evaluation, testing, and modeling Environmental impact assessments Operation Maintenance Turnkey projects City of Sterling, Colorado, USA The City of Sterling planned to construct two 7,000-ft [2,100-m] injection wells to dispose of liquid wastes from a new water treatment plant. The well system designed by a city subcontractor had a target capacity of 350 galus/min [79.5 m 3 /h]. Contracted to drill and complete the wells, Schlumberger used the Platform Express* integrated wireline logging tool and CHDT* cased hole dynamic tester to identify and characterize additional injection zones. Tests confirmed that the additional zones and the application of a site-specific perforating and acidizing program could increase injection capacity to 2,000 galus/min [454 m3/h], a 470% increase over the target capacity. Each well was drilled in a single run and within time and cost constraints.

4 EVALUATE THE SUBSURFACE TO ENHANCE INJECTION PERFORMANCE The performance of an injection well system depends on accurately locating and characterizing the injection and confining zones. Schlumberger is a global leader in advanced subsurface technologies that reduce rig time by performing multiple measurements and collecting fluid samples in a single wireline run. Borehole geophysical logging Schlumberger not only ran the first borehole geophysical logs in 1927, it remains the industry leader in this field through a program of continuous enhancement of in-house expertise and technologies. Geophysical logs are used to aid subsurface characterization, to identify shale zones that provide zonal isolation, and to determine the injection zone properties such as thickness and porosity. Formation testing Cost-effective formation testing is a vital part of injection well system evaluation. Analyzing pressure changes over time, especially changes associated with small variations in fluid volume, can provide information on formation size, shape, damage, and ability to take in fluids. Schlumberger is a leader in pressure transient analysis and step testing to determine formation boundaries, hydraulic parameters, and fracture pressures and in evaluating the near-wellbore region for formation damage. The MDT* modular formation dynamics tester enables collection of multiple fluid samples during a single wireline run, rapid pressure measurement, and vertical and horizontal permeability measurement. The CHDT* cased hole dynamics tester has the ability to drill through casing into the formation, perform multiple pressure measurements, recover fluid samples, and then restore pressure integrity by plugging the hole made in the casing. Aquifer simulation A successful injection program requires a thorough understanding of what happens to injected fluids. Moreover, numerical simulation of fluid movement may be a key regulatory requirement. Schlumberger experts have deep experience in simulating simple to complex geological conditions. When multiple geological and geophysical data sets, complex reservoirs, and dual-porosity systems require simulation, the advanced workflows are managed using the Petrel* E&P software platform and ECLIPSE* industry-reference reservoir simulator with the H 2 O extension. MDT modular formation dynamics tester. City of Hialeah, Florida, USA Schlumberger designed, obtained permits for, and supervised the construction and testing of two Class I injection wells for the disposal of concentrate and other liquid wastes from the City of Hialeah reverse-osmosis water treatment plant. The injection wells are 3,500 ft [1,068 m] deep and each has a design capacity of 7.39 million galus/d [28,000 m 3 /d], giving the plant 100% backup capacity. Collaboration with government agencies and the simultaneous construction of both wells and an associated dual-zone monitoring well enabled the project to keep to a tight schedule to receive a funding grant. The Hialeah injection well system was completed on time and within budget.

5 OPTIMIZE INJECTION WELL CONSTRUCTION AND MAINTENANCE The long-term performance and reliability of an injection well system depends on careful attention to all aspects of its design, construction, and operation. Schlumberger has extensive experience and expertise in all aspects of injection well management feasibility assessment, design, well drilling, engineering, supervision, logistics, procurement and contracting of third parties, and drilling rig management. Accurate well placement Schlumberger uses its aquifer characterization technologies to identify the most suitable injection zones for optimal well performance. Well placement teams steer and maintain the well trajectory to maximize exposure to the injection zone. Advanced logging-while-drilling services acquire real-time high-quality data for geosteering and formation evaluation while measurementwhile-drilling services deliver the data in real time at transmission rates that are quadruple the industry standard. Clean perforations for enhanced injection For many injection wells, a perforated completion is the preferred design. Optimization of the perforation program can be the least expensive means to significantly improve well performance. The PURE* clean perforations system minimizes or eliminates perforation damage, taking into consideration the rock type, formation porosity, and formation permeability to produce the cleanest possible perforations. The result is efficient communication between the reservoir and wellbore. Sand control for long-term viability To protect formation integrity in the long term, a screen or liner might be required. Schlumberger experts use Sand Advisor* screen and gravelpack planning software to select the optimal sand control design that achieves uniform injection pressure along the wellbore. The software analyzes the formation particle-size distributions against its extensive database to recommend screen and gravel sizes. Well stimulation to improve fluid flow When low permeability or near-wellbore formation damage limits the injection rate, hydraulic fracturing and matrix stimulation treatments can increase or restore injection well capacity. A wide range of treatments is available to address all types of formations while minimizing costs. For example, the HiWAY* flow-channel fracturing technique significantly increases fracture conductivity while reducing water and proppant consumption. The result is higher short- and long-term injectivity, simpler logistics, and a smaller operational footprint. Rehabilitation of old wells Most injection wells require occasional rehabilitation (workover) to maintain or restore performance. Schlumberger technologies include the CT EXPRESS* rapid-deployment coiled tubing unit, which provides speed, economy, and a small footprint. Operated with two trucks and a three-person crew, the unit has a rig-up time of less than 30 minutes. The PowerCLEAN* engineered fill removal service can be deployed to efficiently clean out sands and other solids and Jet Blaster* engineered high-pressure jetting service applies focused high-energy fluid streams to loosen compact fill while reducing the risk of damage to downhole installations. Smith Ranch-Highland Mine, Wyoming, USA Cameco Resource s Smith Ranch-Highland mine in eastern Wyoming is the largest uranium mine in the US. Schlumberger provided turnkey construction of three new injection wells and performed workovers on two existing wells to convert them into Class I injection wells. Well completion involved perforation and hydraulic fracturing. A well cleanup program was key to removing proppant and fracturing fluids prior to injection testing. Cameco received a successful turnkey solution, resulting in an injection well system that exceeded the required injection rates and volumes. The project adhered to an aggressive schedule and was completed within budget.

6 Injection Wells for Liquid-Waste Disposal Long-term reliability and environmental protection Schlumberger experts have decades of experience working with customers to deliver both routine projects and complex solutions that use advanced technologies. Schlumberger recognizes that balancing the needs of the project, the technology solution, and the customer s cost performance expectations is integral to achieving successful injection wells for liquid-waste disposal. slb.com/liquid-waste *Mark of Schlumberger Other company, product, and service names are the properties of their respective owners. Copyright 2016 Schlumberger. All rights reserved. 16-WS-0003