Study On Solidification Treatment Technology Of Waste Drilling Mud

Waste drilling mud is one of the major pollutants produced in oil & gas field exploration and development. If disposed with improperly, waste drilling mud would certainly enter the environment and pollute local environment that results in inestimable loss. Then, the development of petroleum industry will be in turn restricted by environmental pollution. Based on the origin analysis origin, the pollutant characteristics, and the present state of processing technology of waste drilling mud and Combining the analysis of actual conditions in production area in northern Shaanxi Changqing Oilfield, the studies have analyzed the pollutant characteristics of waste drilling mud comprehensively and put forward curing-after-gel breaking technology with ferric salt and composite solidified agent composed of fly ash, quicklime, loess soil and cement. Effects of all kinds of factors on waste drilling mud solidification results have been investigated. The mechanism of solidifying treatment has been studied, too. A few of meaningful results have been achieved as follows:(1) Based on site investigation and analysis experiment, the waste drilling mud after the well finish from production ares in northern Shaanxi Changqing Oilfield is the ropy fluid state. This ropy colloid has completely no free water, sizable viscosity, and high water content. The chroma, COD_Cr content, pH value, oil, suspended matter content of waste drilling mud are much higher than those regulated in standards. Moreover, orgnic contaminant component is extremely complicated and its toxicity is much higher. If handled improperly, waste drilling mud will cause enormous hazard to the environment. Therefore, the research of treating waste drilling mud is imperative.(2) Combining the characteristics of CMC and the principle of curing mud, an innocuous treatment process of waste drilling mud is put forward, i.e. carry out gel breaking pretreatment at first, and then join composite solidified agent with fly ash and loess as main material to solidify Waste drilling mud. In this way, through pozzolanic activity of fly ash and cementation of loess soil it will have a certain degree of compression strength and become the denser solid.(3) The type of gel breaker has been selected and the optimum dosage has been determined through experimental study. By comprehensive consideration of water quality of centrifugate of waste drilling mud and mud-cake water content, four types of gel breaker are selected. The results of solid-liquid separation effect of them are as follows: ferric chloride > ferric sulfate > polymerization aluminum chloride > aluminum sulfate. Therefore, the choic of gel breaker for waste drilling mud is ferric chloride. The optimum dosage of ferric trichloride is that 1 cubic meters of waste drilling mud is dealt with by adding 0.006 tons ferric chloride.(4) Based on gel breaking pre-treatment of waste drilling mud, taking the chroma, COD_Cr content, pH value of lixivium and compressive strength of solidified body as the main indicators, the optimum dosage of solidification raw materials is obtatined by orthogonal experiment: 1 cubic meters of waste drilling mud is dealt with by adding 0.4 tons fly ash, 0.06 tons lime, 0.4tons loess soil and 0.05 tons cement. The solidified agent can immobilize the waste drilling mud effectively. The solification time and compressive strength can be controlled through controlling the dosage of solidified agent, thus controlling the solidification effect. The results of Innocent evaluation experiments indicate that the contamination contents of lixivium can be superior to the first class standard of Integrated Wastewater Discharge Standard (GB8978-1996). In this way, the damage caused by waste drilling mud is greatly reduced, thus realizing the objective of in situ fast solidification treatment.At the same time, effects of all kinds of factors on waste drilling mud solidification results are analyzed in detail. The results can offer some technical references for dealing with waste drilling mud of other area. The mechanism of all kinds of solidified agent is explored, too.(5) The treatment technology of waste drilling mud has been designed preliminarily and the cost analysis and economic evaluation of raw materials used have been made. The results indicate that the solidification technology proposed has some practical and economic value. It will lay the technical foundation for further field application.