importance of managing environmental performance throughout the entire drilling and completions process. Reducing the presence and/or environmental impact of drill cuttings may be essential for obtaining market access, complying with regulations, and avoiding possible remediation costs. Complying with environmental laws and regulations is business critical as non-compliance may result in either the inability to drill or substantial fines. Regulatory controls minimize the impact of permitted discharge of cuttings based primarily on toxicity. Laws and regulations vary by location. On US land, for example, waste requirements typically originate at the state level for oil and gas exploration and production while the Environmental Protection Agency is the primary regulatory agency for environmental concerns (API 2011). In addition, many of the local watersheds and ground water protection agencies are either at a multi-state level or a river basin level (EPA 2012). Offshore, national government agencies regulate the permitted discharge of cuttings to prevent unreasonable degradation of the marine environment. Depending on the drilling location, the target level of non-aqueous fluids on cuttings typically ranges from 0% to 8%. In recent years, regulations governing the treatment and disposal of drill cuttings have become more stringent with multiple areas moving towards complete zero discharge (Figure 1).
Maintaining Social License to Drill
The rising power of local community stakeholders— particularly in US land, where individual landowners maintain subsoil ownership rights—may have greater impact on our industry today than ever before. Now, the ability to conduct oil and gas drilling is subject to opinions of outside parties in addition to environmental laws and regulation. In today’s technology-driven world, everyone has access to information. Traditional news outlets are no longer the sole opinion leaders. Everyone has the ability to create and disseminate information, fact-based or not. In some cases, this can contribute to more entrenched environmental opposition, especially in ecologically and socially sensitive areas like those described above. How environmental risks are perceived and regulated has impacted access to oil and gas reserves worldwide. Today, public opinion helps determine the ability to obtain and maintain drilling permits. A company that is not conscientious of its environmental impact and/or working to mitigate may be subject to losing its social license to drill (Kitasei 2011).
Technologies Delivering Operational and Cost Benefits Along with Improved Environmental Performance A central challenge surrounding the implementation of select
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environmental technologies is ensuring efforts to reduce the environmental impact intrinsic in oil and gas development do not negatively impact operational and cost performance. For waste management, technologies that reduce the amount of drill cuttings and/or treatment required before disposal achieve this balance. The technologies discussed below demonstrate how business and environmental goals can be achieved in parallel, proving that technology decisions made on the basis of performance and bottom-line dollars can also deliver legitimate environmental gains.
Drilling Tools for Wellbore Stabilization Reduce Amount of Cuttings Generated While Drilling
When a drill bit deviates from the desired well path, drillers must reduce the pressure applied to the drill bit and make frequent adjustments to the bottom hole assembly (BHA) to steer the bit back to the desired course. These corrective actions consume valuable drilling time and result in crooked oversized wellbores for drilling efficiency losses estimated as high as 200%. Through the use of rotary steerable systems and similar low-cost alternatives, drillers can maintain verticality in the wellbore and recover the lost time and cost. They can also reduce the amount of environmental waste by an estimated 30% through decreased cuttings and fuel consumption. Therefore, along with well-accepted efficiency gains, drilling straighter wells delivers positive environmental impact by reducing drilling waste from the source.
Centrifuges and Dryers Reduce Presence of Non-Aqueous Fluids on Cuttings
Drilling fluid type and local discharge requirements (in terms of the permitted level of non-aqueous fluids on cuttings) help determine the method for cuttings disposal offshore. For cuttings with non-aqueous fluids, the main options include: Ó Cuttings re-injection into existing or new wells Ó Shipping cuttings onshore for treatment and disposal Ó Offshore discharge following treatment (Tullow Oil 2009). While cuttings re-injection and shipment are the preferred methods for zero discharge environments, in environments where offshore discharge is allowed centrifuges and dryers offer operational and cost efficiencies along with environmental performance. Centrifuges separate fine drilled solids from the drilling fluid. Doing so prevents drilled solids volume from exceeding a threshold level in the drilling fluid that could inhibit the drilling process and/ or damage additional rig equipment. When drilled solids increase above the acceptable threshold level, the only way to reduce the solids to fluid ratio to acceptable levels involves dumping and diluting the fluid.
