Case Study: Highly Inhibitive Water-Based Fluids Help Operator Optimize Performance and Cost While Meeting European Environmental and Regulatory Goals
Authors: Dormán J. , Aldea C. , Marinescu P. 
Published: December 2007

Planning a well nowadays means not only addressing technical issues like trouble-free drilling and reducing formation damage, but also seriously considering the amount and type of waste that will be generated, local environmental regulations, options and costs for waste disposal, and last but not least, cost effectiveness. Add to all these considerations the continuous demand for improving drilling performance, safety compliance, higher targeted production rates and quicker well completion.

To achieve all these targets, a novel concept of integrated services program was started in Hungary in 2002. Since then, more than 15 wells have been drilled successfully under this approach, using different types of inhibitive muds. Reducing overall drilling waste volumes by more than 25% per year while complying with European, local Hungarian regulations, and the operator's targets was always among the strict benchmarks.

Aligning all of the fluid-related services has been attempted before. It is an objective of many service companies. However, in this case aligning the services was only one of the primary considerations. The approach was to achieve that objective while using the same conventional inhibitive mud systems, lower mud and waste volumes, and drill faster in more challenging situations. At the same time, there was a need to develop new water-based systems that could perform like oil-based muds in areas were oil-based mud is technically necessary, but is prohibited for environmental reasons.

To achieve all these targets, a novel highly inhibitive water-based mud was used for the first time to replace the conventional potassium chloride/glycol or amine-based drilling fluid in Hungary. The fluid reduced significantly the drilling time, eliminated the non-productive time (NPT), generated fully in-gauge wellbore, and reduced project costs. Generated waste was lower using this approach than for offset wells. Fluid formulation was flexible enough to be adapted for the high-temperature environment expected on the second interval. Extensive laboratory work allowed the appropriate fluid formulation to be chosen and led to the inclusion of sodium formate in this type of fluid for the first time.

This paper details the design and performance of a highly inhibitive water-based fluid that is a dual inhibition mud system formulated for maximum shale inhibition, and is potassium free, optional chlorides-free and high-temperature stable to 150°C. The degree of inhibition provided by the system is significantly greater than any other water-based system and truly approaches the level of performance of an oil-based system.

The authors will discuss also the environmental restrictions applying to drilling waste management in highly-populated central European onshore environments and their implications on well planning and waste management concepts and the field results showing the successful implementation. Key Performance Indicators (KPIs) were defined at the beginning of the project to measure performance. The project resulted in substantial and sustainable reductions in drilling waste generation while at the same time improving drilling performance through optimized drilling fluid systems, enhanced rates of penetration, and consistent gauge-hole performance in soft to medium-hard sediments.

Laboratory work and results are also provided to illustrate the fluid optimization undertaken in preparation for this job.