Drilling fluids environment

Scale deposits create conditions for concentration-cell corrosion as they do not form uniformly over the metal surface. Sulfate-reducing bacteria thrive under these deposits, producing hydrogen sulfide and, consequently, increasing the rate of corrosion. Due to the following factors, the drilling fluid environment is ideal for scale deposition [189]. These factors are as follows ... 

Alkalinity Control. Water-base drilling fluids are generaHy maintained at an alkaline pH. Most mud additives require a basic environment to function properly and corrosion is reduced at elevated pH. The primary additive for pH control is sodium hydroxide [1310-73-2] in concentrations from 3 to 14kg/m (1—51b/bbl). 

The rotary drill bits are generally made from quench and tempered steel alloys such as AISI 3115 to 3120, 4620, 4815 to 4820 and 8620 to 8720. The only corrosion related problem that can arise may result from a hydrogen sulfide environment. The bearing in the roller rock bits can be damaged by H S contamination of drilling fluid. However, a well conditioned drilling fluid at... 

Linear polarization instruments provide an instantaneous corrosion-rate data, by utilizing polarization phenomena. These instruments are commercially available as two-electrode Corrater and three electrode Pairmeter (Figure 4-472). The instruments are portable, with probes that can be utilized at several locations in the drilling fluid circulatory systems. In both Corrater and Pairmeter, the technique involves monitoring electrical potential of one of the electrodes with respect to one of the other electrodes as a small electrical current is applied. The amount of applied current necessary to change potential (no more than 10 to 20 mV) is proportional to corrosion intensity. The electronic meter converts the amount of current to read out a number that represents the corrosion rate in mpy. Before recording the data, sufficient time should be allowed for the electrodes to reach equilibrium with the environment. The corrosion-rate reading obtained by these instruments is due to corrosion of the probe element at that instant [184]. 

A prestressed roller bearing is used to detect the presence of hydrogen sulfide, but more specifically it is used to test for hydrogen embrittlement tendency of the drilling fluid. When introduced to the environment, the bearing has sufficient residual stresses to cause failure if sufficient hydrogen sulfide concentration is present. 

J. M. Getliff and S. G. James. The replacement of alkyl-phenol ethoxy-lates to improve the environmental acceptability of drilling fluid additives. In Proceedings Volume, volume 2, pages 713-719. 3rd SPE et al Health, Safety Environ Int Conf (New Orleans, LA, 6/9-6/12), 1996. 

On the basis of the indirect investigations and in eompliance with the prescriptions of the Italian Environment Ministry, environmental investigations were carried out at the refinery using eontinuous eore recovery drilling (water was used as the drilling fluid for a total of approximately 2,700 linear meters of drilling. A total of 50 Lugeon... 

Bakhtyar, S., Gagnon, M.M., Webb, D., Nguyen, K. and Rabke, S.P. (2011) Closed-bottle biodegradation test for synthetic-based drilling fluids under Australian conditions. Global J. Environ. Res., 5 (1), 21-31. 

Sprague JB, Logan WJ. 1979. Separate and joint toxicity to rainbow trout of substances used in drilling fluids for oil exploration. Environ Pollut 19 269-281. 

Chronic Effects of Drilling Fluids Discharged to the Marine Environment... 

Drilling fluid products that are to be disposed of from offshore platforms and landfill sites must be tested for their effects on animal and plant life. Components that have been identified as potentially toxic and hazardous to the environment are oil (diesel or mineral), heavy metals (Cr, Hg, Zn, Pb, etc.), and chlorides. 

In addition to the above fimctions, the clay minerals used in the drilling fluid are environment-friendly. Being highly stable in the environment prevailing over or near the surface of the earth, fliey do not undergo any chemical alteration or release any pollutant or contaminant in the environment. This aspect of clay minerals is discussed in Section 17.6 (Part 111). 

In rural environments, storage pits may be used to hold water. They are typically excavated containment ponds that, based on the local conditions and regulatory requirements, may be lined. Pits can also be used to store additional make-up water for drilling fluids or to store water used in the hydraulic fracturing of wells. 

---