11. Solids control

Good solids control equipment is a requirement for any drilling operation. The level of oil on cuttings for both OBM and synthetic mud discharges has been the focus of a great deal of attention in the cuttings discharge debate and the solids control industry has responded by developing equipment that will greatly reduce the oil on cuttings (OOC) compared to simple shale shaker processing. Although there is no mechanical equipment able to reach the 1% oil on cuttings (OOC). It is recommended that adoption of the highest performance solids control quickly becomes a requirement for operations planning to use and discharge synthetic mud.

A standard arrangement of linear shale shakers will typically leave an oil on cuttings (OOC) level of 10 - 15%. The level is usually lower in top hole sections where cuttings are large and higher in lower sections where cuttings hold down effects and greater residence time in the borehole often result in finely ground cuttings. Improved solids control can reduce this oil on cuttings (OOC) level to 5% or better at relatively low cost, effectively halving the amount of synthetic mud discharged on cuttings. Furthermore the additional mud recovered may represent a substential saving per well section, making it attractive in financial as well as environmental terms.

It is recommended that the use of this kind of solids control technology and other performance enhancing equipment, such as the active flow divider to replace the header box, be pursued on a rig specific basis with the solids control companies.

As well as reducing the amount of synthetic mud discharged on cuttings it should be recognised that significant surface losses of synthetic mud result from other sources such as shaker overflow, centrifuge waste and disposal of cement contaminated mud. All of these waste streams should be targeted for reduction.