The Maintenance And Treatment Of Drilling Fluids In Gypsum-salt Formation

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:

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Solids Control Equipment for an Un-weighted Drilling Fluid System

The un-weighted muds are the ones that do not contain any weighting materials such as barite or lead sulfide. This is the type of mud that is usually used for drilling shallow formations. The cuttings comprise active solids like clay that hydrate and inert solids like sand, silt, limestone, feldspar and small quantity ofAmerican Petroleum Institute (API) barite. Apart from the API barite which may be used for density control, the other solids are abrasive, and tend to increase frictional pressure loss during fluid flow, increase viscosity and form thick permeable cakes. This may lead to stuck-pipe, excessive torque and drag, lost circulation, and poor cementation. The inert solids are removed from the drilling fluids by using solids control equipment like shale shaker, desanders, desilters (hydrocyclones and decanting centrifuges) in that order. The active solids, like clays, are removed by using chemical flocculant or by diluting the fluid with water.

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Evaluate The Efficiency Of Solids Control Equipment

The volume and type of solids in a drilling mud system can adversely affect mud properties, reduce penetration rates, cause damage to drilling equipment, and increase total drilling costs. Efficiency controlling the solids content of the mud system is an important phase of an efficient and cost-effective drilling program. The three basic methods of removing solids are dilution and/or displacement of whole mud, settling and mechanical solids-control equipment.

Fig 1. Size capacity and operating of solids control equipment

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