Abstract

As the worldwide consciousness concerning environmental protection evolves along with the technology, the need for new methodologies to dispose of oilfield wastes in a safe manner grows under tight governmental regulations and careful management of risks, liabilities and costs. This is particularly true for remote areas such as deep water and environmentally sensitive locations where there is a strong emphasis on protecting the natural resources of the drilling area. Accordingly, many regulatory agencies demand zero-discharge policies and require all generated wastes to be disposed in a responsible manner. Such a process involves the adequate management of by-products generated during drilling operations including cuttings, excess drilling fluid, contaminated rainwater, produced water, scale, produced sand, and even production and cleanup waste. Old practices involve temporary box storage and hauling of the waste products to a final disposal site. Often, these practices create not only liabilities for the operating company but also environmental risks such as accidental spills, gas emissions and eventually, high operating costs.

Waste Injection (WI) into sub-surface formations has proven to be the most effective technology for final disposal of wastes from oil and gas drilling and production that provides a secure operation achieving zero discharge. WI achieves this by storing the injected material several meters below surface in hydraulically created fractures, avoiding surface environmental risks and future liabilities for operating companies.

This paper presents the methodology based on risk analysis, supported by successful worldwide case histories, to prepare an operational and cost-efficient operation that continuously analyzes information and provides fit-for-purpose recommendations to achieve a seamless injection process. The Assurance Waste Injection process permits the detection and identification of potential risks giving mitigation options to prolong the life of the injector.

Introduction

Wastes generated during drilling and production processes in the oil industry need to be safely disposed of in a permanent manner to avoid any contamination to the environment. Implementing a waste management system to support operations allows planning for the reduction of waste streams generated by reusing or recycling some material and the use of different options for treatment or disposal of the waste either at surface or into the sub-surface. The last option, sub-surface injection or Waste Injection (WI), allows for a safe and permanent waste placement into a receiving formation downhole. This methodology for final disposal is widely accepted around the globe as it accomplishes the zero discharge demanded from the regulators, with lower gas emissions compared to other technologies, low costs and minimal risks especially in large scale remote projects. The development of the WI technology started at the end of the 80's, but injecting small volumes of slurry through the tubing of dedicated disposal wells or the prepared annulus of production wells. However, experiences on sub-surface studies and on operations gained through the years has increased the injection volumes from thousands of barrels in the 80's to over 20 million barrels in 2008. WI operations can be performed worldwide independently of weather conditions, rig type, waste volumes and drilling operations, with the planning stages of consideration of risk management and mitigation options, the important keys for the safety and success of the operation.

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