Mixed Waste In Northern Oilfield Drilling Microbial Situ Remediation Technologies

The intermixture of drilling waste,which is mainly composed of waste drilling-mud, waste drilling water,drainage,cuttings and fracturing flow-back fluid,is the blending contaminants yielded during the exploit and exploration procedure of petroleum and natural gas.It was classified as a sort of toxic solid waste which contains large mounts of pollutants such as petroleum and heavy metal ion.The biggest environment risks generated during the exploration of petroleum and natural gas were largely due to it.Directly towards the contaminants within the intermixture of drilling waste,the present study was undertaken to screening a certain group of microbes with ability of contaminants degradation in high efficiency.Through the metabolism of microbe groups,contaminants within the intermixture of drilling waste could be degraded effectively and the environment risk generated during the exploration of petroleum and natural gas can be vanished.30 isolates of microbe strains were isolated from 23 samples of different sources by Plate Dilution method.5 isolates with high ability of contaminants degradation were screening from these 30 isolates.Through the traditional bacterial systemic identification method and the analysis of 16S rDNA &18S rDNA sequence,the 5 strains were respectively identified as Bacillus,Acinetobacter,Rhodococcus,Pseudomonas and Glomus.According to the characteristics of strains,the compound solid inoculant which contains all 5 strains was developed to obtain higher degradation efficiency.The experiment result showed that the total counts of microbial reached 10¹⁰/g within a short time after the inoculation when the environmental temperature＞10℃.Strains could make the contaminants within the intermixture as the only nutrients source to get themselves grew As well as each strains obtained a better grow activity due to the corporations between the strains.Through the metabolism of microbe groups from the compound solid inoculants, contaminants within the intermixture of drilling waste obtained a great degradation.After 30-60 days degradation,the total content of petroleum hydrocarbons in the intermixture were reduced at the level of 95%;the content of Cr⁶⁺ was reduced by 99%;pH were changed from＞10 to 6.5-7.5;the total counts of microbial reached 10¹⁰/g;the content of water changed to 40%-60%;even the content of organic matter could increase 300%according to these in the soil.The contents of main contaminants in the intermixture of drilling waste were reduced at a great level;the characteristics of intermixture were changed to make new possibility for planting.The aim to minimize the risk of intermixture to the environment was perfectly met.After experimental work in lab,On Site Microbial Ecological Recovery experiment was carded out in YuLin and WuQi at the northern of Shaanxi province.After 30-60 days,the all 58 mud pit which ecological recovery experiments carded out were got through the examination from Environmental Protection agency from local government.The recovery results indicated that the microbial method could effectively remediate the intermixture of drilling waste under the natural environmental condition in the northern of Shaanxi province.