The injection of drilling generated waste into a selected subsurface formation has evolved into the most preferred waste disposal technology in terms of environmental compatibility and cost effectiveness, especially for remote and environmentally sensitive areas. The main principle of waste injection (WI) is the initiation of hydraulic fracture and the placement of solids within the created fractures through the high-pressure pumping of slurry batches. The fracture propagation is governed mainly by in-situ stresses. As injection progresses solids accumulation in the fracture leads to an increase of in-situ stresses within the injection zone causing a build-up of injection pressure. As allowable injection pressure is often limited by equipment, the undesirable or rapid injection pressure build-up could jeopardize the operational life of an injection well and limit its waste disposal capacity. This paper introduces a new approach to a regular seawater injection by investigating the relationship between pressure behavior and seawater injection. Displacement of slurry from the tubing by seawater over flush is carried out routinely in WI operations worldwide. However, never before it was considered as a pressure maintenance tool. The authors describe the impact of continuous seawater injection on injection pressure through the lifetime of three waste injectors. The injection pressure behavior before, during and after continuous seawater injection was reviewed using downhole measured data. It was noticed that regular seawater over-displacements during the continuous time periods between slurry injections reduced injection pressure considerably. Consequently, a thorough evaluation was initiated to investigate the impact of extended seawater injection on in-situ stresses and its potential advantage in maintaining the injection pressure within lower limits. Considering the novelty and value of study for expanding worldwide WI operations, this paper presents the new approach to seawater injection as an injection pressure and disposal capacity maintenance tool. Introduction In the early 1990s, WI emerged as a new technology that could provide an environmentally safe and economically sound solution to the disposal of drill cuttings and associated wastes in environmentally sensitive and remote operations. It was identified as one of the few technologies able to provide a complete drilling waste disposal solution that eliminates the need to accumulate, store and haul cuttings to shore for treatment. First pioneered with small volume annulus injections in the Gulf of Mexico in the mid-1980's the technology has since gained broad use in the North Sea, Alaska and other areas where the environmental conditions, tight regulations and logistics made this a viable drilling waste management option.1, 2 WI has been implemented successfully in the Caspian Sea since 2006, despite a complex subsurface environment and tectonics that presented significant technical challenges for vigilant monitoring and pressure interpretation as injection progresses.3 Pressure follow-up was recognized as critical to ensuring the safe and long-term containment of the waste to be injected.

fax 01-972-952-9435. AbstractThe handling of drill cuttings and wastes is both an environmental and economic issue in drilling operations. With ever-tightening environmental regulations and the green operation initiatives of operators, drill cuttings re-injection (CRI) into a subsurface geology often is the preferred option as it allows operators to achieve zero discharge since oily cuttings are returned to their place of origin.When the technology started about a decade ago, injection into a single well had a maximum slurry volume of approximately 30,000 bbl. Now, particularly in very large projects, several million barrels of slurry may be injected into a single well. This represents more than a 1000 times the volume of a typical hydraulic fracturing job or more than 100 times that of those earlier cuttings re-injections. In some cases, the success of the CRI operation is critical because there either are no back-up options or the economic and environmental impacts are too significant. This paper describes the challenges faced in CRI projects, along with recent advances and experiences gained in tackling these challenges through modeling, cuttings slurry and operational procedure design, monitoring and verification. For example, much progress has been made recently in slurry rheology design and operational procedure selection such as suspension/displacing to avoid loss of injectivity and to maximize disposal capacity and minimize HSE issues.The authors also will present a risk-based approach, which integrates deterministic software and tools, available data, knowledge and experience, for modeling of geological and operational uncertainties and potential risks to increase the quality assurance. Case examples will be presented to illustrate the value of this integrated approach. Best practice guidelines and recommendations will be provided on data collection, design and engineering, operation and monitoring.

fax 01-972-952-9435. AbstractThe progression of new field developments, including brownfield and deepwater, subsequently increases the volume of cuttings and production waste, and particularly produced water, considerably. The economical impact of missing drilling and production targets due to the failures in the drilling waste injection process represents high risks that demand sound engineering processes to ensure injection assurance.This paper describes the solution and detailed pressure monitoring methodology implemented to maintain safe injection assurance via regular disposal fracture diagnostics. Timely identification and a thorough evaluation of non-ideal pressure signatures observed during injection and post shut-in periods provided critical information required to detect subsurface anomalies. This can be an effective tool for the subsurface risks identification and characterization.The application of comprehensive fracture-mapping techniques is a major step in mitigating the environmental risks posed by waste. Waste mapping represents valuable information, not only in the overall planning of drilling operations, but in the fundamental and invaluable need to provide sound engineering for waste location and fracture containment assurance, thus minimizing environmental impact. Previous, oversimplified interpretations of multiple fracturing systems (or so-called uniform disposal domain) and new fracture initiation process are demonstrated to be in apparent conflict with fracture mechanics, stress calculations and the general principles of physics.The authors also describe the results of pressure analysis conducted in a North Sea injection well, which simultaneously was used for production. The well was utilized successfully for Cuttings Re-Injection (CRI) and for the disposal of produced water. The success of the operation was a direct result of close monitoring of key injection parameters and indepth analysis of injection pressure, despite risky geological conditions. Abnormal pressures increases and restrictions observed during injection were mitigated and addressed via a proper root-cause engineering and sound pressure diagnostic process. The drilling waste injection took place below a 13 3/8-in. casing shoe through the B annulus, in an open-hole section at the depth of 1220m TVD with a 24 0 deviation in the injection interval. The injection took place in close proximity to a major fault axis.

The South part of the Priobskoe field, located in Western Siberia on a flood land of the Irtysh River, is an environmentally sensitive area. Zero discharge regulations prohibit cuttings discharge and spills of liquid wastes on the surface. Until now, the exploration and full development of such oil and gas fields was a major challenge for operating companies working in Russia as all drilling wastes including cuttings, used muds ready for disposal, and waste waters which cannot be disposed in this sensitive area. Drilling wastes had to be transported away from the region to areas where waste disposal pits were allowed to be constructed and wastes to be stored. The major hurdle for the drilling campaign is the cost of transportation of the vast amount of drilling waste generated from multiple rigs. Moreover, during spring or fall, such transportation is virtually impossible because of the absence of winter roads and rivers are impassable due to flooding or ice movement. A joint effort between a major oil company in Russian and a waste management service company selected Waste Injection (WI) technology as the most efficient, economical and environmentally friendly way to handle the drilling waste in the field. Waste Injection is a relatively new waste disposal methodology used in Russia, although the first injection job on a worldwide basis was in 1991. The first Russian WI operation was successfully implemented in 2004 on offshore projects near Sakhalin Island. Since that time and until October 2008, WI had only been used on several offshore platforms. The need of a robust technology for waste management on the South Priobskoe field was the departure point for implementing WI in mainland Russia. The following paper describes the steps taken to implement WI on land projects in Russia as the technology that allows for zero discharge, ensuring a safe and permanent drilling waste disposal performed under strict regulations and minimizing associated transportation and cost risks. Waste Injection Assurance Most of the oil companies in Russia wanted to implement WI on the mainland but were concerned about legislation issues as this type of operation had never been done on Russian land jobs. In October 2008, the first steps towards making WI operations a reality in Russia began with the development of a feasibility study or Front-End Engineering Design (FEED) Study for waste injection in the area, as part of the assurance process.

Summary The handling of drill cuttings and other wastes generated by drilling operations is both an environmental and economic issue. With ever-tightening environmental regulations and the green operation initiatives of operators, drill cuttings reinjection (CRI) into subsurface geology is often the preferred option, allowing operators to achieve zero discharge because oily cuttings are returned to their place of origin. When the technology was introduced about a decade ago, injection into a single well had a maximum slurry volume of approximately 30,000 bbl. Now, particularly in very large projects, several million barrels of slurry can be injected into a single well. This represents more than 1,000 times the volume of a typical hydraulic fracturing job, or more than 100 times that of earlier cuttings reinjections. In some cases, the success of the CRI operation is critical, either because there are no backup options or because the economic and environmental impacts are too significant. This paper describes the challenges faced in CRI projects, along with recent advances and experience gained in tackling these challenges through modeling, cuttings slurry and operational procedure design, monitoring, and verification. For example, much progress has been made recently in slurry rheology design and operational procedure selection such as suspension and displacement to avoid loss of injectivity and to maximize disposal capacity and minimize health, safety, and environment (HSE) issues. The authors will also present a risk-based approach that integrates deterministic software and tools, available data, knowledge, and experience, for modeling of geological and operational uncertainties and potential risks to increase quality assurance. Case examples will be presented to illustrate the value of this integrated approach. Best-practice guidelines and recommendations will be provided for data collection, design and engineering, operation, and monitoring. Introduction Oil and gas E&P companies are responsible for recycling, storing, or disposing of drilling wastes in a safe and environmentally acceptable fashion that complies with regulatory requirements. Tightening environmental legislation worldwide and operators' environmental policies are reducing options for disposal or are increasing discharge costs to the extent that discharging of drilling wastes may not be a future option. Injecting drilling and other associated E&P wastes through hydraulic fracturing has been successful and has led to the adoption of the technique as a routine disposal method. CRI operations started in the late 1980s with small volumes of drill-cuttings slurry using either tubular or annular injections (Abou-Sayed et al. 1989; Malachosky et al. 1993; Minton and Secoy 1993; Sirevag and Bale 1993; Moschovidis et al. 1994; Willson et al. 1993; Louviere and Reddoch 1993). However, as more experience was gained through these smaller-volume waste disposal operations, the scale of drill-cuttings injection operations increased dramatically (Schmidt et al. 1999; Baker et al. 1999; Guo et al. 2003). For example, in terms of disposal volumes, by 2002 CRI operations had increased from thousands of barrels of slurry per well to millions of barrels per well (Guo et al. 2003). CRI operations moved from onshore to offshore fixed platforms to deepwater mobile offshore drilling modules (Abou-Sayed and Guo 2002; Minton and Secoy 1993; Saasen et al. 1998; Saasen et al. 2001). It has been operated worldwide within a wide range of different environments. A drill-cuttings injection operation involves the collection and transportation of waste from solids-control equipment on the rig to a slurrification unit, where the cuttings are ground (if necessary) to small particles in the presence of water to form a slurry. The slurry is then transferred to a holding tank for final rheological conditioning. The conditioned drill cuttings slurry is pumped through a casing annulus or tubing into subsurface fractures created by injecting the slurry under high pressure into the disposal formation. The waste slurry is often injected intermittently in batches into the disposal horizon, followed by a period of injector shut-in. Each batch injection may last from less than an hour to several days or even longer, depending upon the batch volume and the injection rate.