Slag Mix Mud Conversion Cementing Technology: Reduction of Mud Disposal Volumes and Management of Rig-Site Drilling Wastes

Abstract

Blast furnace slag is a unique hydraulic material which is a by-product of the steel-making process. A new method of mud to cement conversion technology utilizing slag as the hydraulic material has been developed, and the technical merits of this slag mix are briefly reviewed. This slag mix technology is economically, technically, and environmentally superior to conventional Portland cements and has been used in many fields. The major environmental benefit is the reduction of mud disposal volume. Since the application of slag mix at Prospect Auger in the Gulf of Mexico, excess whole mud discharge has been reduced by about 70% (4,530 barrels per well). Approximately 15,000 barrels of excess drilling mud was recycled into slag mix at Auger. In addition, a new drilling waste management method to reduce or eliminate drilling waste at the rig-site has been developed. A new type of slag-supplemented drilling fluid containing 40 to 60 lb/bbl slag can produce slag-laden cuttings which are self-setting with time. The in-situ solidification method seems to be environmentally acceptable and potentially cost-effective. Introduction Drilling waste management is a growing concern for the industry. Current drilling fluid and cuttings disposal methods are being challenged by an increasing number of federal, state, and local regulatory agencies. The drilling industry is therefore seeking more environmentally acceptable and cost-effective methods for drilling fluid and drilled cuttings disposal. Excess drilling fluid can be converted to a cement using slag (1) to provide an improved seal in the annulus between the borehole wall and casing and (2) to provide adequate structural support for the casing. For simplicity, this in-situ mud conversion technology will be referred to as slag mix or slag-mud slurry in this paper. The objective of this paper is to present the environmental advantages of slag mix technology and to demonstrate the technical merits of a new drilling waste management method using slag. A unique waste management concept was formally introduced by Congress as a regulatory concept in the 1984 Hazardous and Solid Waste Amendments to the Resource Conservation and Recovery Act (RCRA) of 1976. The 1980 RCRA amendments exempted oil industry exploration and production (E and P) wastes from regulation under the RCRA Subtitle C (40 CFR 261-265) hazardous waste provision. Subtitle C identifies hazardous chemicals in two ways - by listing and by definition. One group of wastes exempted from regulation as hazardous waste is drilling fluids, drilled cuttings, produced water, and other waste associated with crude oil and natural gas exploration, development, and production. Since most E and P wastes are non-hazardous, they are regulated as subtitle D (40 CFR 256-257) solid waste under RCRA and the regulations of the various oil-producing states. While the exemption lifts many of the burdens of RCRA Subtitle C (hazardous waste) requirements, it remains the operator's responsibility to assure adequate protection through proper waste management practices. The goals of the RCRA program are to encourages solid waste management practices that (1) promote environmentally sound disposal methods, (2) maximize the reuse of recoverable resources, and (3) foster resource conservation. P. 443^

Other Potential Applications for Alkali-Activated Materials

“…Alkali-activated BFS formulations for this application were initially developed by Shell Oil Co. in 1991 for use in the Gulf of Mexico, and similar mixes have also been successfully used in China [ 48 ] and Brazil [ 49 ]. The Shell product, named 'Slag-Mix', was used as a complete replacement for Portland cement-based well cements on several projects in the Gulf of Mexico in the 1990s [ 45 ], and was reported to show technical, environmental and economic benefi ts compared to Portland cement in this application [ 46 ], including application as a 'universal fl uid' to provide both drilling fl uid and cementing behaviour [ 50 ]. Work reported from the laboratories of some other oil companies [ 51 ] did show that under some circumstances, alkali-activated BFS slurries were prone to cracking and variability between mixes, which has to some extent limited their more widespread use throughout the industry.…”

Study of Low Density and High Strength Slag MTC System

“…Although the problem of displacement efficiency has been researched a lot, the displacement efficiency is hard to improve due to the defect of common cement slurry [3][4][5][6][7][8][9][10] . For improving the cementing quality, the technology of mud converted to slurry (MTC) was generated, which could solidify the mud by stimulating the activity of the slag using the alkali [11][12] . The MTC could improve the cementing quality significantly, and the hydration mechanism of MTC was studied in paper [15] .…”