Gumarov, Salamat (Schlumberger) | Benelkadi, Said (Schlumberger) | Bianco, Eduardo (Schlumberger) | Woolf, Shaun (Schlumberger) | Hardy, Chris (Schlumberger) | Ido, Hisataka (ADOC Japan) | Tanaka, Manabu (ADOC Japan) | Tominaga, Naohiro (ADOC Japan) | Yahata, Kazuhiro (ADOC Japan) | Okuzawa, Taker (ADOC Japan)
Management of drilling wastes presents major challenges during drilling operations in environmentally protected areas. An Abu Dhabi offshore field development project selected cuttings reinjection (CRI) services as an appropriate solution for waste management.
Although CRI is a proven technology in the region, fracturing injection always inherits its own containment-related risks. To prevent all possible failures that were experienced earlier in the industry globally, a novel real-time monitoring and analysis of fracturing injections data was introduced.
A comprehensive front-end engineering design (FEED) study was performed to evaluate the feasibility of CRI techniques by selecting a suitable injection formation and designing a CRI-dedicated well, surface facilities, slurry testing, and appropriate operations execution plan.
The CRI well was drilled and completed to accommodate waste volumes. An assurance program based on industry best practices was used to support zero solids settling, fracture, or perforation plugging.
To achieve on-time intervention, the first real-time CRI data transfer through a satellite-based network to a support center staffed by global experts in Abu Dhabi was deployed to analyze fracture injection and shut-in pressure responses for early identification of possible risks and to map the fracture waste domain.
The project has been operated successfully since its inception with more than 300,000 bbl of drilled cuttings and drilling waste fluids injected since July 2016. No injectivity issues were experienced during drilling waste fluids injection. Several on-time interventions had been made to prevent well plugging and to maintain surface injection pressures within normal ranges.
Real-time data streaming has made a step-change improvement in the data delivery process, monitoring, and fracture pressure analysis. It creates a direct link between the wellsite and worldwide multidisciplinary technical expertise centralized in Abu Dhabi and provides visualization capability at any time and to any where to all personnel involved in the project.
This step change in monitoring CRI operations provides an acquisition-to-answer" integrated solution, mitigates the injection risks, and enhances the intrinsic value of CRI services.
The paper shares the experience of implementing the novel real-time CRI subsurface injection assurance program dedicated for cuttings reinjection operations. Real-time support from multidisciplinary experts provides live injection monitoring and fracture waste domain mapping for highly complex and risk-prone subsurface injection environments with stringent regulations
Haddad, Mohamed (ADNOC Offshore) | Rashed Al-Aleeli, Ahmed (ADNOC Offshore) | Toki, Takahiro (ADNOC Offshore) | Pratap Narayan Singh, Rudra (ADNOC Offshore) | Gumarov, Salamat (Schlumberger) | Benelkadi, Said (Schlumberger) | Bianco, Eduardo (Schlumberger) | Mitchel, Craig (Schlumberger) | Burton, Phil (Schlumberger)
Injection of drilling waste into subsurface formations proves to be an environmentally-friendly and cost-effective waste management method that complies with zero discharge requirements. It has now become the technology of choice in offshore Abu Dhabi.
The aim of cuttings reinjection (CRI) is to mitigate risks associated with subsurface waste injection and reduce cuttings processing time and cost. In order to meet these goals, a cuttings reinjection subsurface assurance methodology was developed to improve cuttings processing and continuously monitor drilling waste injection operations.
Preparing for CRI operations required extensive drilling cuttings slurry testing to minimize processing time and develop optimum particle size distribution to reduce cost and increase the injected waste volume. The improvements were accompanied by downhole pressure and temperature monitoring of the injection well, thus facilitating analysis of injection pressures. Fracture containment was verified through a combination of pressure decline analysis, periodic injectivity test, temperature survey, and periodic modelling for fracture waste domain mapping. A backup injection well was used also as an observation well to monitor the pressure signitures in the injection formation.
More than 1 million barrels of drill cuttings and associated drilling waste have been safely and successfully disposed of into a single injection zone of CRI well over three years of operations.
The cuttings reinjection subsurface assurance method optimizes grinded cuttings particle size distribution, detects and identifies potential risks to provide mitigation options to prolong the life of the injector.
The proactive subsurface injection monitoring-assurance program was built into the fit for purpose CRI injection procedure to continually avoid injecting any rejected hard material, improve and update the process as per subsurface injection pressure responses, thus reducing processing time and cost, mitigating injection risks, and extending the injection well life.
This paper presents the unique and technically challenging cuttings slurry properties design and pressure interpretation experience learned in this project; the enhancement of cuttings processing helped increase injection volumes and an in-depth interpretation of fracture behavior which behaved like a risk-prevention tool with mitigation options. Significant enhancement was developed in slurry treatment procedures to avoid injectivity loss and maximize the disposal capacity.
Mehtar, Mohammed (Abu Dhabi Marine Operating Company) | Haddad, Mohamed (Abu Dhabi Marine Operating Company) | Toki, Takahiro (Abu Dhabi Marine Operating Company) | Gumarov, Salamat (M-I SWACO, a Schlumberger Company) | Benelkadi, Said (M-I SWACO, a Schlumberger Company) | Shokanov, Talgat (M-I SWACO, a Schlumberger Company) | Vizzini, Carla (M-I SWACO, a Schlumberger Company) | Mitchell, Craig (M-I SWACO, a Schlumberger Company) | Khudorozhkov, Pavel (M-I SWACO, a Schlumberger Company)
This paper examines the challenges, solutions and milestones of the hydraulic fracturing based cuttings reinjection (CRI) process implemented on two artificial islands offshore Abu Dhabi.
During the development of an offshore field from two artificial islands, disposing of vast amounts of drilling waste and cuttings, generated from almost 100 wells, presented a major challenge. The conventional skip-and-ship for onshore treatment and disposal was technically, logistically, and economically unviable and posed possible future environmental liability. After careful assessment, total containment of drilling waste on the islands through multiple hydraulic fractures in suitable formations, for permanent in-situ waste confinement, was concluded by the operator as environmentally and economically the only sustainable process.
Two CRI wells were planned on each island to accommodate an estimated 8 million barrels of drilling waste slurry expected to be generated at the islands. While CRI is a proven technology wherein cuttings are slurrified and injected into sub-surface formations, fracture injections have high risks too. Many failures are known in the industry, including well and formation plugging and waste breaches to sea-bed and near-by wells, with far-reaching consequences and liability to operators.
Considering the complexity of the multiple-hydraulic fracturing process that requires careful planning, execution, monitoring, and analysis, a comprehensive geomechanical study was performed to identify and characterize all potential injection formations to achieve successful long-term injection. This was followed by front-end engineering design (FEED), fracture simulations, CRI well design, surface facilities design, slurry simulations, and followed by careful execution.
Two CRI wells were drilled on each island. Specifically designed injectivity tests were performed on each well before commencing injection, followed by regular injectivity tests to continuously analyze fracture behavior. A carefully designed slurrification and injection process, incorporating detailed QA-QC at all process stages, was implemented that helped to avoid solids settling, fracture or perforation plugging, uncontrolled fracture propagation, or well integrity issues. About 500,000 barrels has been successfully injected to-date in two CRI wells with injection pressures as per FEED estimates.
The paper details also the proactive sub-surface injection monitoring-assurance program built into the CRI injection procedure to continually modify the process as per sub-surface pressure responses, thus proactively mitigating injection risks.
Periodical injectivity tests, model alignment studies, temperature logs, and fracture pressure analysis facilitated regular recalibration of the geomechanical model to define fracture-domain sizes, monitor fracture height growth, and estimate residual formation domain capacity as injection progressed.
The multiple-hydraulic fracture-based CRI process implemented first time in Abu Dhabi incorporates many unique features which can be applied in similar projects elsewhere. This paper also describes the downhole gauges for accurate pressure-temperature monitoring at perforations, a detailed slurry design, the particle-size distribution for slurry quality analysis and quality control, the sub-surface monitoring-assurance program and regular tests and recalibration studies.
Waste generated during exploration, development, and production of oil and gas fields are required to be disposed in a responsible and environmentally friendly manner. Over the years, environmental regulations governing the disposal of such waste have tightened and each day regulatory agencies are demanding more stringent policies, especially for remote and environmentally sensitive areas. Waste Injection (WI) has been proven over the past decade to be the safest and most efficient technology for final disposal of waste materials such as produced water, drill cuttings, spent drilling and completion fluids, scale waste, NORM, produced sand, production and well cleanup waste. This cost-effective technology complies with the strict environmental guidelines, such as the ones governing zero-discharge environments. More regulatory agencies are gradually recognizing WI as a robust solution to safe and assured final disposal of waste generated in upstream and downstream sectors of the oil industry.
WI has evolved from a simple pumping operation, with lack of sub-surface understanding, to an assured process that has integrated the knowledge from all areas of the operation: engineering design, equipment and operational parameters, monitoring, and quality control-quality assurance. This continuous assessment guarantees a cyclic process that identifies potential risks at early stages, and allows proper management and mitigation to prolong the life and integrity of the operation.
This paper presents the unique and technically challenging injection monitoring and pressure interpretation experience attained in different WI projects worldwide, where the in-depth interpretation of fracture behavior helped as a risk-prevention tool with mitigation options applied to operational parameter well specifics. The continuous monitoring of injection data and parameters assists in developing a well history and a prediction mechanism for well storage capacity, extending the life of the injector and maximizing efficiency for the development of the field.
WI continues to be implemented on a worldwide basis. It provides a safe, permanent and economical solution for drilling and associated service and production waste disposal at remote asset developments while meeting strict regulatory guidelines. When WI is implemented as a disposal methodology, it requires an investment by the operator in three key areas: 1) activities for front-end planning, 2) provision of surface equipment, and 3) the conduit to the disposal formation, normally a dedicated WI well. The degree of investment necessary for each area may be gauged by establishing an "assurance factor?? that is justifiable based on the project economics, i.e., what should be spent to mitigate risk to adequately ensure the proper degree of success for the project. One of the main drivers in the development of the assurance factor is production of first oil or gas on or ahead of schedule.
In additional to this approach, investment may be made to enhance operations and optimize the usable life of the injection well, further assuring or improving the economic performance of the project. This is in the form of "monitoring?? of WI operations. This assurance process brings value by constantly capturing data, providing analysis and constantly reporting improvement suggestions to procedure. A comprehensive monitoring program requires installation of surface (and optionally subsurface equipment) to collect and log data, and analysis and reporting of information back to the project owner and operations group. Besides optimization of operations which may allow faster rate of penetration (ROP), reduce processing hours or prolong pressure experience within the limitation of infrastructure, actions from monitoring may extend the life of the
dedicated injector well, saving rig time associated with well service and/or allowing use of an additional well slot for production rather than disposal.
Hydraulic fracturing generally has been limited to relatively low-permeability reservoirs. In recent years, the use of hydraulic fracturing has expanded significantly to high-permeability reservoirs. The objectives of fracturing low-permeability reservoirs and high-permeability reservoirs are defined by reservoir parameters.
The estimation of reservoir permeability, a variable of great importance in hydraulic fracturing design, is frequently unknown because either candidate wells do not flow or pretreatment pressure-transient testing is required. Consequently, Nolte et al.1 introduced a new method for adding after-closure fracturing analysis to the pretreatment calibration testing sequence that defines fracture geometry and fluid-loss characteristics. The exhibition of the radial flow is ensured by conducting a specialized calibration test called the minifalloff test. Using the theory of impulse testing and the principle of superposition, Nolte et al.1 developed a method that allows the identification of radial flow and, thus, the determination of reservoir transmissibility and reservoir pressure.
This work proposes a new method for determining reservoir permeability. The method also offers the potential for determining the average reservoir pressure. This procedure is based on the use of the pressure derivative, and it requires only one log-log plot for the identification of the radial-flow regime and the determination of reservoir parameters.
The application of the proposed method is demonstrated on real field data from calibration tests performed on several oil and gas wells. The reservoir parameters (particularly permeability) determined with this method are verified by comparison with results obtained from pressure-buildup tests. Other sources, such as core analysis, lend support to the permeability estimated with the proposed technique.
Hydraulic fracturing has generally been limited to relatively low-permeability reservoirs. In recent years, the use of hydraulic fracturing has expanded significantly to high permeability reservoirs. The objectives of fracturing low permeability reservoirs and high permeability reservoirs are different and defined by reservoir parameters.
The estimation of reservoir permeability, a variable of great importance in hydraulic fracturing design is frequently unknown because candidate wells either do not flow or a pretreatment pressure transient test is required. Consequently, Nolte has introduced a new method for adding after-closure fracturing analysis to the pretreatment calibration testing sequence that defines fracture geometry and fluid loss characteristics. The exhibition of the radial flow is ensured by conducting a specialized calibration test called mini-fall test. The derivations by Nolte, based on the theory of impulse test and principle of superposition, allow the identification of radial flow and thus the determination of reservoir transmissibility and reservoir pressure.
This study presents a review of the after-closure radial flow analysis. A modified method is proposed to complete the Nolte's method for the determination of the reservoir transmissibility and reservoir pressure based on the pressure derivative.
The application of the modified method is demonstrated on actual field data from calibration tests performed on several oil and gas wells. The reservoir parameters determined with this method are verified by comparison with results obtained from buildup tests.
Hydraulic fracturing has been recognized to be an effective means for enhancing well productivity and recoverable reserves, especially for low permeability reservoirs, by reducing the resistance to flow area between the wellbore and formation.
The appropriate fracturing treatment for a given well has been hard to design because of the numerous variables involved. The use of inaccurate reservoir variables to design treatments may lead to poor production estimates.
In wells that are to be hydraulically fractured, minifracture treatment, called also calibration test, frequently is performed to determine parameters needed for the stimulation design. It is generally performed without proppant and therefore, retains negligible conductivity when it closes.
Fracture pressure analysis was pioneered by Nolte1,2. The basic principles are analogous to those for pressure analysis of transient fluid in the reservoir. Both provide a means to interpret complex phenomena occurring underground by analyzing the pressure response resulting from fluid movement in rock formation.
The analysis of fracturing pressure, during injection, during closing and after closure period, provide powerful tools for understanding and improving the fracture process.
Advances in minifracture analysis techniques have provided methods for determination of fracturing treatment design parameters such as leak-off, fracture dimensions, fluid efficiency, closure pressure and reservoir parameters. These parameters can then be used to determine the pad volume required, best fluid loss additives to be used, and most importantly, to achieve the optimum fracturing treatment design.
Fig. 1 shows a typical history of the calibration test from the beginning of pumping until the reservoir disturbance from the fracture decays back to the initial reservoir pressure.
Fracturing pressures during each stage of fracture evolution (i.e. growth, closing and after-closure) provide complementary information pertinent to the fracture design process. Therefore, Fracturing pressure analysis may be reduced to three distinct types of analysis.