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Field Experiences With Oilfield Waste Disposal Through Slurry Fracture Injection

Sipple-Srinivasan , M ., Bruno , M ., Bilak , R ., and Danyluk , P . SPE 38254, SPE 67 th Annual Western Regional Meeting , Long Beach, CA (1997)

This paper was prepared for presentation at the 67th Annual Western Regional Meeting of the SPE held in Long Beach, CA, U.S,A., 23-27 June 1997.

Abstract

More than 100 years of extensive oil production in the U.S. and Canada has resulted in the generation of large volumes of Oilfield waste, including produced oily sands and tank bottoms, drilling muds and cuttings, and crude contaminated surface soils. Much of this oilfield waste is the result of previous practices in which drilling muds and even produced oil were impounded in unlined storage pits. Many areas have also been contaminated due to spillage around well cellars, tank farms, and pipe yards. The Los Angeles Basin alone contains more than 10 giant oil fields (100MM bbls or larger) which together are estimated to have created more than 2 million cubic meters of crude contaminated soils. In addition to this pre-existing source of oilfield waste, ongoing production operations continue to produce large quantities of drilling muds, tank bottoms, and produced oily sands. A significant portion of the pre-existing and annually generated oilfield waste material is currently being stored on-site until operators are forced to deal with the wastes whether due to regulatory pressure or in order to convert the property to other uses.

An economic and environmentally sound technique to dispose of these produced oilfield wastes is to re-inject them back into the subsurface. The Slurry Fracture Injection (SFI) process involves slurrification of oilfield wastes with produced water and re-injection at fracture pressures into appropriate formations at the oil field where the waste was generated. On-site disposal of oilfield wastes provides four major advantages to the oilfield operator. These are:

l) An environmentally attractive permanent disposal solution.

2) Little impairment of surface land use.

3) Reduction of long-term liability to waste generator.

4) Reduced transportation and disposal costs.

Terralog Technologies is currently managing slurry fracture injection projects at several sites in the US and Canada, disposing of produced sands, pit sludges, tank bottoms, and crude contaminated surface soils. Typical disposal volumes are on the order of 4,000 to 8000 bbls of slurry waste per day, per well. This paper presents a summary of Slurry Fracture Injection facilities, technical design considerations and monitoring techniques, and regulatory issues in the US and Canada. Two field examples are presented and described in detail.

Introduction

Permanent, low-risk disposal of Non-hazardous Oilfield Waste (NOW) can be achieved through injection of a slurry comprised of waste material and produced water into deep permeable geologic formations. Waste generated at an oilfield location can often be re-injected at fracture pressure through existing wells into the same subsurface formations from which the wastes originated.

The process of Slurry Fracture Injection (SFI) is a means to dispose of accumulated oilfield wastes by deep well injection. This process yields considerable advantages to the operator over conventional disposal methods. SFI provides an environmentally attractive and permanent disposal solution for considerable volumes of NOW waste, and has minimal impact on surface land use. In addition, it affords a significant reduction of long-term liability to the operator while reducing transportation and disposal costs. Traditional alternatives to SFI disposal include road spreading, surface disposal or landfills, incineration, soil washing, and disposal into salt caverns. These methods are generally more costly and leave the operator susceptible to future environmental and other liability concerns. Other potential solid waste streams can also be considered for disposal using this technique. Naturally Occurring Radioactive Materials (NORM) present in produced water, scale, and sand from oilfields in many regions such as the Gulf Coast of the U.S. are a good candidate for disposal.

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