TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractHydraulic 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.

Summary 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.

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.

The progression of new and remote field development, including arctic and deepwater, inherently increases the volume of cuttings and waste generated from drilling, completion and production operations. The economic and environmental impact of this waste management including transportation, treatment and final disposal is considerable and can be drastically decreased through subsurface cuttings and waste injection. This environmentally friendly disposal solution provides an effective and practical way to minimize associated health, safety and environmental risks by eliminating transportation needs and potential accidents, and therefore reducing the long-term project environmental footprint.Nowadays, cuttings injection is considered a proven technology for the final disposal of drilling waste through subsurface injection into an engineered subsurface strata or formation where the injected waste is safely contained for permanent storage. The logistical constrains of transporting large volumes of produced waste to the final disposal site poses many challenges in large-scale field development, where the most cost-effective solution is often to drill a dedicated injector well, process and inject all the produced waste at the single cuttings injection site.An application of comprehensive fracture-mapping techniques is a major step in ensuring that the target formation will be suitable to accommodate all waste volume injected. Fracture mapping the waste domain complexities represents valuable information, not only in the overall planning of drilling operations, but in the fundamental and invaluable need to provide sound engineering and assurance for the waste subsurface containment.This papers describe the driving factors and opportunities for implementing cuttings injection in one of the largest and complex development projects in the northern part of Caspian Sea where ecologically sound drilling, stringent environmental regulations and "zero discharge" policy commitment are critical for the success of the drilling operations and overall field development.

Drilling waste generated during development of oil and gas offshore and onshore fields are required to be disposed of in a responsible and environmentally friendly manner. The remoteness of such environments, coupled with the ever-tightening environmental regulations and then green operation initiatives of operators, can create significant economical, logistical and regulatory challenges. The subsurface drilling cuttings reinjection becomes the preferred option allowing oil and gas operators to achieve zero discharge which can meet the most stringent environmental standards. To prevent all possible injection issues that were experienced earlier in the industry globally (early 1990's), a novel "design, execute, evaluate approach was introduced, this enables us to deliver reliable, single sourced start to finish solutions Subsurface drilling waste injection has been and continues to be used on several offshore projects where many millions of barrels of waste have been injected in a single well. This has been achieved through the engineering approach "design, execute, evaluate". The design study assesses the subsurface strata and identifies suitable injection zones, with a focus on waste containment assurance. The execution and evaluation phase begins with an initial injectivity test to calibrate all the reinjection modelling completed so far, we then implement real time injections surveillance including advanced pressure analysis as a risk control tool. The key focus is to analyze, identify, and recommend necessary adjustments during injections to prevent injection failure. The studied cases have been operated successfully since their start to date. No injectivity issues have been experienced during drilling waste fluids injections. Several on-time interventions have been made to proactively prevent the well becoming plugged and maintaining surface injection pressures within normal ranges. Recent advances of Real-time data streaming have made big step change improvement in the data delivery process, monitoring pressure analysis. It creates a direct link between the wellsite and worldwide multidisciplinary technical expertise and provides visualization capability at anytime and anywhere to all personnel involved in the project. This step change in monitoring drilling cuttings reinjection operations provides truly "Acquisition to Answer" integrated solution, mitigates the injection risks and enhances the intrinsic value of drilling cuttings reinjection on offshore development projects. This paper shares the experience and the success of subsurface drilling cuttings reinjection where wastes are injected for final and responsible disposal. The offshore field cases are presented to illustrate the value of the recent technological advances along with best practice guidelines and recommendations for safe and economical disposal of drilling waste fluids to achieve true zero discharge results.