Successful Drilling of Oil and Gas Wells by Optimal Drilling-Fluid/Solids Control— A Practical and Theoretical Evaluation

Abstract

Summary Since the development of the drilling industry, the process for removing drill solids from the drilling fluid has culminated in the use of shaker screens as the primary or sole solution. It is, therefore, necessary to optimize both filtration efficiency and the screen life to hinder drilled solids from entering the drilling fluid. Optimum solids control can be obtained by using knowledge of how damage to the filtration cloth arises, of how to reduce it, and of how the particles in the circulation system influence the general picture of the drilling process. When this knowledge is accepted, established, and implemented in the drilling industry, it is possible to maintain efficient drilling. This paper describes, in detail, the theory and field examples on how wear arises on the shaker-screen cloth. As will be shown, this knowledge has been used to increase the solids-control efficiency and to reduce the screen wear by more than 90% in several field cases where 17½-in. sections have been drilled with oil-based mud. This has been achieved by use of a different screen configuration, running with top screens with finer cut points than normal. This leads to removal of 90 to 95% of the solids from the fluid using the top deck, thereby minimizing the wear on the finer bottom-deck screens. The documentation is based on practical offshore results from these drilling operations, including data from the drilling log, laboratory analyses of the drilling fluid, and of the particle-size distribution (PSD) of the drilling fluid. The particular focus of this article is the application of double-deck shakers. Introduction Correct use of solids-control equipment is essential to maintain drilling fluid within its desired properties and to avoid generation of unnecessary waste streams during drilling (Bouse and Carrasquero 1992). Since the early 1930s, the shale shaker has been the dominant device for primary solids removal (AADE 1999). Additional equipment such as desilters, desanders, and centrifuges were often used in the past to maintain proper solids control. Although it is dependent on the choice of correct shaker screens, most shakers at present perform sufficiently to be able to act as the sole solids-control device without the use of desanders and desilters. The optimum solids-control design for a particular drilling fluid may not be generally valid for all fluid types (Lal and Hoberock 1988). For example, a combination of shaker and screens applicable for treating water-based drilling fluids may not be suitable for treating oil-based drilling fluids. Furthermore, the suitability of the screen and shaker combination may change during drilling because the drill-cuttings morphology changes. During the last few decades, major shaker-design improvements have been made. The circular-motion shakers used up till the 1980s have been replaced by elliptical-motion and linear-motion shakers. Furthermore, double-deck, or even triple-deck, shakers have been implemented in the industry. Alternatives to shakers have been tested to improve occupational hygiene aspects although this type of equipment has not yet reached the market (Saasen et al. 2003). Sinusoidal-formed screens have been implemented on some shakers to increase the flow capacity (Neidhardt 1995). Shaker operation has also been automated (Scott 2006). Scott (2006) claims that use of this automated system leads to an increase in shaker-screen life. However, Scott (2006) does not reveal the screen selection for this case. Therefore, it is difficult to use this information in the present analysis. Removal of solids with a particle diameter larger than 120 to 150 µm can be achieved without problems on most shakers today by the application of the correct screen size (Wollherr and Krobok 1998). There are many types of screens on the market. The following analysis is general and does not compare any products or designs.

A methodology for identification of a suitable drilling waste handling system in the Arctic region

“…Higher viscosity means slower flow and mixing rates, and consequently reduced performance of the waste minimisation systems. To address the above-mentioned problems and minimise the impact of cold temperature on the waste minimisation systems, Dahl et al (2012) and Dahl et al (2006) proposed waste minimisation techniques by optimising the performance of solids control systems in the Arctic environment. Moreover, Kroken et al (2014) presented a fluid management vacuum conveyor system, that eliminates the traditional mechanical process of shaking the fluids and solids and consequently reduces the waste.…”