Optimizing Drilling Waste Treatment to Meet Discharge Criteria

Abstract

Regulations governing offshore discharge are increasingly stringent and diverse, varying between country, legislative framework and type of discharge. One major waste stream is the slop generated during the drilling operation, which is collected in the rig drain systems or in surface pits. The slops come from multiple sources, vary widely in composition and are therefore challenging to treat to meet the discharge regulations of a global market. Slops are formed when drilling or displacement fluids, wash water from routine cleaning operations or rain water runoff become contaminated with drilling fluid components. The slops are captured, either in surface pits or through the rig drain system and collected in storage tanks. Chemical and physical treatments can be used to treat this stream to minimize the volume and cost of disposal, but due to the complex and varied nature of the slop stream, treatment methods must be tailored. Optimal solutions should treat the stream to recover and recycle any drilling fluid. Water should be separated and treated to meet the discharge criteria. In this way the total volume of waste requiring disposal can be significantly reduced. This paper will present a review of the discharge criteria relating to drilling slop waste, highlighting the variations seen between countries. The paper will discuss how this variability, together with the slop chemical characteristics, impacts optimum treatment methods. Examples will be provided of successful treatments of a variety of slop wastes, where both chemical and physical treatment was successfully applied to meet a range of discharge criteria from oil content to complex organic analysis. Understanding slop treatment and the multitude of discharge regulations that can be applied will permit the optimal solution for slop treatment to be selected to minimize waste and maximize reuse whilst ensuring compliance to the required environmental regulations.

Drilling waste minimization in the Barents Sea

“…This also generates a considerable quantity of slop. Depending on geographic location, operational practices and rig configuration, the daily volume of drilling slop can vary from 100 to 500 barrel per day (Mueller et al, 2013).…”

“…For this aim detailed information about characteristic and behavior of subsurface formations is vital. This includes information about; composition and physical properties of the formations; accurate location of the reservoir; fluid migration and distribution; thickness of different formations; subsurface geological features (such as fault, fold, and salt domes) (Mueller et al, 2013). There are different sources where such data can be acquired, such as previous drilled or abandoned wells (i.e.…”

“…It can also result in an optimized well plan such as cementing and completion operations. This finally results in a reduction in final drilling waste in terms of minimized drill cuttings, minimized drilling and completion fluid, cement, etc (Mueller et al, 2013.…”

“…This is of the particular interest, where subsurface formation consists of multiple small zones at different depths that need several vertical wells to achieve the designed recovery rate. In multilateral wells, they share the upper portion of the well and the upper portion of each well is larger in diameter than the lower portion of the same well and this reduce volume of drill cuttings (Peter, 2008, Mueller et al, 2013. Some formations are thin and extends over a huge lateral area by using horizontal drilling expands over this area can recover more and avoids a number of unnecessary vertical drilling.…”

“…Some formations are thin and extends over a huge lateral area by using horizontal drilling expands over this area can recover more and avoids a number of unnecessary vertical drilling. Moreover directional and extend-reach drilling in different directions or to different depths from one main well requires fewer drilling facility and generate less drilling waste (Mueller et al, 2013.…”