Cost Effective and Ecologically Sound Fluid Disposal During Well Clean up and Post Fracturing Flowback Operations

Abstract

An important aspect of the well test and poststimulation flowback operations is the need to produce, responsibly manage, and safely dispose of the substantial amount of hydrocarbons, typically through flaring, which is potentially an environmental concern. This challenge has received significant attention over the past few decades and remains a major concern today. It is especially important in offshore environments, considering requirements for safe disposal of large volumes of crude and gas as well as completion fluids and possibly formation water. A common alternative to offshore flaring is storing the crude on the drilling rig, test barge, or tanker. The methods used for fluid disposal during offshore operations were reviewed as the basis for defining a practical workflow to select the optimal operations design, thus leading to a significant reduction or full elimination of burning. Inaccurately selected fluid disposal strategies can significantly constrain operations, limiting achievable objectives and increasing the risk of HSE incidents. The typical methods employed include fluid storage at the well site, high efficiency burners, and the transfer of produced liquids to oil tankers during extended well tests. Additional considerations from traditional approaches relate to the evolution of regulatory and legal frameworks on environmental concerns. Each method has its benefits and practical limitations. An analysis of possible approaches to avoid burning fluids and minimizing operational limits to well test operations identified that starting from a certain volume, crude storage and the transfer to production facilities can be considered as the best option to avoid burning while adding value to well effluents and turning well tests from a cost-to revenue-generating activity. Focusing on offshore operations with limited deck space and thus potentially limited storage capacity, the solution developed for the North Sea involved transferring the produced crude into a small shuttle tanker via a soft wall surface floating rubber hose. By using a floating transfer hose, the special requirements for hose installation were avoided, saving valuable rig time. It also reduced the need for pipe preheating and enabled the tanker to move, decreasing petrol consumption for maintaining dynamic positioning. The paper will summarize the results and lessons learned from the application of different methods used for fluid disposal in a wide range of well test operations around the globe. These were used to determine that economical and environmentally responsible solutions exist for fluid disposal during well test operations. The paper will also detail an innovative, field-proven, and cost-effective fluid storage solution using a shuttle tanker during well test and flow back operations offshore. This technique was applied in five successfully performed well tests in the North Sea, storing more than 50,000 barrels of reservoir crude in total.