Environmental Impact Assessment of Heavy Metals in Surface Disposed Drilling Waste

Saudi Arabia has some of the biggest oil and gas reserves in the world, and has expanded its drilling operations gradually to meet the global demand. Improper handling of contaminated drilling wastes may cause serious negative environmental impacts. The current study investigates the toxicological effects of heavy metals in drilling waste by quantification and developing different contamination indices. Solid and liquid samples from different drilling waste pits were collected and analyzed for heavy metals. The average concentration varies significantly and decreases in the order of Fe > Al > Sr > Mn > Cu > Cr > Zn > Ni > Pb > Cd > Ag > Co. The spatial variation showed the highest concentration at SDGM Site 1, West. Comparison of current data showed continental crust average values within the specifications for most of the sites. For metals like Cd, Cr and Cu, the concentration is higher than the continental crust value. Indices such as pollution load index, modified degree of contamination etc. were calculated from the available data. The contamination level for different site calculations showed nil to a very low degree of contamination. Spatial variation of the contamination level indicated comparatively higher values for sites UTMN-4 and SDGM-1 North, which indicates the necessity of precautionary methods. The metal concentration in the pit water samples exceeded generally accepted standards, if this water was to be discharged/leaked from the pit. The current study concluded presence of different heavy metals in samples from the drilling waste pits, whereas the degree of contamination is minute.

Study on Hardening and Reuse Technology of Drilling Waste

In order to meet the increasingly strict environmental requirements and achieve the comprehensive utilization of waste in drilling operation,three techniques were used to harden the drilling waste.The three techniques are cement hardening technology,fly ash hardening technology and quicklime-sodium silicate hardening technology.Orthogonal analysis was used to evaluate and optimize the experimental results from the three techniques.The results show that the hardening system of quicklime-sodium silicate is not satisfying,and the compressive strength of hardened body is only 1.32 MPa.The optimal mass ratio in cement hardening system is drilling waste∶water∶YHJ1∶YHJ2∶YHJ3∶cement = 10∶4∶3.2∶2.2∶0.5∶4.The optimal mass ratio in fly ash hardening system is drilling waste∶water∶YHJ1∶YHJ2∶YHJ3∶fly ash = 10∶4∶3.2∶1.8∶1.5∶2.The compressive strength reaches 3.19 and 2.95 MPa respectively.Based on this strength,the hardened body can be used as low-strength building bricks,subgrade or nutrition bowls in arid regions to achieve the reuse of drilling waste.

Performance Analysis of a Profile Control Agent for Waste Drilling Fluid Treatment

A method for the treatment of hazardous waste drilling fluids,potentially leading to environmental pollution,is considered.The waste drilling fluid is treated with an inorganic flocculant,an organic flocculant,and a pH regulator.The profile control agent consists of partially hydrolyzed polyacrylamide,formaldehyde,hexamethylenetetramine,resorcinol,phenol,and the treated waste drilling fluid itself.For a waste drilling fluid concentration of 2500 mg/L,the gelling time of the profile control agent is 25 h,and the gelling strength is 32,000 mPa.s.Compared with the profile control agent prepared by recirculated water under the same conditions,the present profile control agent displays better stability,salt-resistance,and performance.

Soil microbial response to waste potassium silicate drilling fluid

Potassium silicate drilling fluids （PSDF） are a waste product of the oil and gas industry with potential for use in land reclamation. Few studies have examined the influence of PSDF on abundance and composition of soil bacteria and fungi. Soils from three representative locations for PSDF application in Alberta, Canada, with clay loam, loam and sand textures were studied with applications of unused, used once and used twice PSDF. For all three soils, applying ≥40 m^3/ha of used PSDF significantly affected the existing soil microbial flora. No microbiota was detected in unused PSDF without soil. Adding used PSDF to soil significantly increased total fungal and aerobic bacterial colony forming units in dilution plate counts, and anaerobic denitrifying bacteria numbers in serial growth experiments. Used PSDF altered bacterial and fungal colony forming unit ratios of all three soils.