New Computer Model Optimizes Solids Control
Authors: Sharples Virginia , Nance Gary W. 
Published: December 2007

Increased drilling costs have prompted the development of a new computerized model drilling program. Solids Control Optimized Program for Equipment (S.C.O.P.E.) is an innovative computer program which is used as a planning tool for optimizing the mud and equipment planning tool for optimizing the mud and equipment profile and as a basis for projecting well costs for mud profile and as a basis for projecting well costs for mud and equipment.

The program is used to determine what means of mechanical separation best meets the needs of a particular well site and to calculate water consumption and amount of mud to be jetted in anticipation of ecological requirements. These factors, estimated by S.C.O.P.E., are compared with actual data reported from a Louisiana well.

(The program listing is too lengthy to be included in this paper; however, input data forms and the reports they generate will be made available to the drilling industry upon request.)

Introduction

According to the Cost Study Committee of the Independent Petroleum Association of America, total drilling Petroleum Association of America, total drilling costs per well rose 14.7% last year, with drilling mud and additives up 18.6%, increasing faster than any other purchased items on U.S. wells. This trend justifies the development of a system to determine the correct combination of solids control equipment to reduce the overall mud treatment and maintenance costs.

The problem was to design a mathematical model to calculate amounts of materials processed by various combinations of solids control equipment. Also to be included in the calculations were the associated costs of mud and equipment rental based on current figures.

The separation characteristics of each piece of equipment, determined through field tests, are the bases for efficiency ratings within the program. Research of actual well recaps verifies that S.C.O.P.E. closely parallels mud reports for completed wells on which the same solids control equipment was in use.

In comparing S.C.O.P.E. to the most comprehensive recap, underflow and overflow characteristics for each solids control device are shown. The design of S.C.O.P.E. is described, and the program's implementation criteria, value and use are established.

THEORY

S.C.O.P.E. is a mathematical model of a freshwater circulating system. The model represents any drilling rig on which the mud leaves the suction pit in desired condition and is pumped to the drill bit, where drilled solids are added. The mud then flows to the surface and is processed by the solids control devices. It returns to the suction pit, where the mud volume and condition are "treated" to desired properties. A flow diagram (Fig. 1) illustrates the equipment sequence in the program.

The effectiveness of the solids control equipment in use and the prediction of what additional equipment can do are determined through particle-size distribution. To choose the proper equipment, the particle-size in the mud and the return stream from each piece of equipment are analyzed to determine what solids remain and require processing.

The mud content in percent by volume is calculated for every 304.8 m drilled or every 24 hours of drilling time. Fraction of flow rate for water, gel, barite and drilled solids is calculated. These variables are evaluated at the flowline, again past each piece of equipment, and finally at pump suction, where treatment occurs to obtain mud properties specified at the data input stage.

Viscosity is considered to be maintained at the desired level based on the assumption that with controlled maintenance, contaminants can be removed while usable mud components are salvaged in almost every formation drilled.

When drilled solids control methods are not efficient, costs for treating mud to the desired properties increase.