Economic and Performance Analysis Models for Solids Control

An important but often neglected element that has a significant impact on drilling operation is the solids control system. Several papers and case histories have attempted to emphasize the importance of solids control in drilling operations. However, substantial savings possible from more effective solids control are usually not well-understood for the following simple reasons. It is difficult to quantify the economic impact of solids control on various costs such as mud, waste disposal, drilling and trouble costs. The normal method of reporting these costs under several categories in field operations also makes it difficult to document the savings. In the absence of a systematic procedure for selecting appropriate solids control system for a given operation, it becomes hard to justify the need and the extra rental cost for any additional solids removal equipment. The development of analytical tools for the analysis of economics and performance of solids control systems should help in justifying and selecting more effective solids control for drilling operations. Recent environmental concerns regarding the disposal of drilling wastes have given impetus to the development of closed-loop drilling operations. Since closed-loop solids control system is an important element of such an operation, methods are also needed for analyzing the economics and performance of such systems.

In this paper, we address these problems and provide an analytical basis for the economic provide an analytical basis for the economic justification and selection of adequate solids control. An economic analysis model is developed which is based on consideration of several drilling parameters and the material balance equations. The model parameters and the material balance equations. The model predicts the relative savings in mud makeup and predicts the relative savings in mud makeup and wastes disposal costs as a function of percent removal of drilled solids. The model also predicts the economics of closed-loop implementation and the percent solids that need to be removed to achieve percent solids that need to be removed to achieve the closed-loop condition, defined in the paper. Next, an analytical model is developed to analyze the performance of a given solids control system in terms of its solids removal capability. This model is mainly based on consideration of the particlesize and the separation or grade efficiencies of particlesize and the separation or grade efficiencies of various pieces of solids removal equipment in a given system. A case history given in the paper illustrates the field application of these models and describes the successful implementation of closed-loop systems with currently available equipment and technology.

During a drilling operation, drilled solids or cuttings generated at the bit mix and interact with the initially formulated drilling fluid and bring about changes in its density, rheology, and other properties. These changes are affected by such properties. These changes are affected by such factors as the flowrate, density, size distribution and the degradation tendency of the drilled solids. These factors, in turn, are determined by such interacting variables as lithology, fluid properties, penetration rate,, and the wellbore geometry. properties, penetration rate,, and the wellbore geometry. P. 209