Case History: Application of a Novel Workflow to De-Risk, Plan and Execute Efficiently a Drill to Frac Project in North Sea
Authors: Mocanu A. , Bocaneala B. , Norris M. , Channa S. , Verlinden V. , Roberts C. , Dingwall S. , Jones B. 
Published: September 2023

The Southern Sector of the North Sea comprises numerous gas sandstone reservoirs typically exploited by dry tree steel jacketed platforms of 2 - 20 wells. This paper describes in detail the case history of a successfully planned, drilled and hydraulically fractured new well targeting Leman sandstone within an extensive field located 150 km off the UK coast. The objective was to drill a well in a largely unexploited part of the reservoir and use fracturing as a commercial completion in the low permeability Fault Block 1. Due to the unknown and varying characteristics of the underlaying Westoe Formation with sandstones potentially extending into the water leg, and thus providing a conduit for water, coupled with a challenging environment, an efficient team collaboration was of critical importance for the best outcome of the project.

Risks related to hydraulic fracturing operations were extensively explored in the early phase of the project through a detailed study and assessment of the uncertainties impacting the final results. One of the key uncertainties was reservoir proximity to water and associated risk of fracture connection. The target reservoir block is bound by the presence of a fault on the north which imposes additional operational risks. A study using a new and novel uncertainty driven frac design workflow was carried out prior the drilling phase to identify, highlight and quantify the key uncertainty factors with associated risks related to proppant fracturing technical aspects as well as their potential impact on the fracturing outcomes. This allowed technical and operational risks to be effectively managed throughout the project. Expertise of the applicable disciplines were captured through a close collaborative approach coupled with the use of an innovative consensus tool. During the hydraulic fracturing operations, a suite of diagnostic tests was performed followed by three temperature log runs allowing the hydraulic fracture height to be de-risked. Naturally this provided additional inputs for fracturing model calibration and final fracture design adjustments.

The well was successfully drilled and completed with a single proppant fracture from a vertical wellbore through the primary reservoir horizons. The resulting production, with a low BS&W, was in line with the planning projections and forms a detailed and validated dataset for the consideration of future vertical single, or multiple fractured horizontal wells in the field. This project has proven the feasibility of new area development and effectiveness of correctly applied fracturing workflows and techniques in this and other fields in the area.

A novel uncertainty driven frac design workflow was applied at an early planning phase to identify and quantify the key uncertainty factors with associated risks related to proppant fracturing technical aspects as well as their potential impact on the fracturing outcomes. Applicable disciplines and their expertise were captured through a close collaborative approach coupled with the use of an innovative consensus tool to expedite the drive to an optimum solution.