A simple and economical surface solids control method to complement the downhole systems becomes necessary when we desire to reduce viscosity, yield point, gel strength, total solids, concentration of drilled solids, and low micron-size material. This aim will be achieved when we are able to partially reject the undesirable materials from the drilling fluid system.
The use of “dewatering units,” as a regular part of the drilling fluid treatment process on drilling rigs, continues to increase. A dewatering unit, the final phase of a solids control program, is designed to discard no free liquid. A solids control program in which a dewatering unit is used is referred to as a “closed-loop system” (CLS), “sump-less system,” or “chemically enhanced centrifugation” (CEC).
The gypsum-salt formations are complex in drilling fluid. The gypsum-salt formations are characterized by salting-in property, plastic creep and anisotropy. Meantime, the rheological properties of drilling fluids become worse when contaminated by high pressured brine in the gypsum-salt formations. In the process of drilling operation in the long-section gypsum-salt formation, reasonable mud weight and good rheological properties of drilling fluids should be used to ensure the safety drilling in this complex formation. The main matters needing attention is as follows:
A field method for measuring solids sizes on the job. It is simple and easy to use and should improve the efficiency of solids control. There will be some sacrifice in accuracy; however, only the relative weight percentage distribution of the particles is needed to allow constructive steps to remove these particles.