The application of quantitative risk analysis (QRA) techniques for well construction in complex reservoirs West Vanguard Snorre cross-section Øystein Arild, RF – Rogaland Research

Common use of QRA in drilling engineering Well planning process time Start of drilling Drilling & well construction Start of planning QRA Success criteria: Specialized, well specific study Relevant data available Unifying approach Dimensions of risk: Impact on safety Impact on cost, i.e. drilling efficiency

Risk analysis framework ”The challenge is to know how to describe, measure and communicate risk and uncertainty” Terje Aven 1.Focus is placed on quantities expressing states of the ’world’, so-called observable quantities 2.The observable quantities are predicted 3.Uncertainty related to what values the observable quantities will take is expressed by means of probabilities 4.Models in a risk analysis context are deterministic functions linking observable quantities on different levels of detail The world Observable quantities Y, X = (X 1,X 2,…,X n ) Risk analyst’s understanding of the world Background information, including phenomenological knowledge, experience data and operational experience Model Y = g(X) Uncertainty assessments P(X <= x) Simplifications Probability calculus Risk description Prediction of Y Uncertainty assessment of Y, P (Y <= y)

Research programmes and products UBDRisk Risk€ RiskSection KickRisk Sponsors: ENI Norge Norsk Hydro Statoil NPD

Risk management for planning of drilling challenging reservoir sections A platform for handling, discussion and understanding of risk in a well planning setting Improved risk communication between economists and engineers in the project Improved basis for decisions –Alternative well designs –Optimalization of e.g. mud weight Improved decisions and profitability Goals for the development:

Risk management for planning of drilling challenging reservoir sections Background Heavily faulted Stratified Long horizontal sections Different pressure regimes HPHT Deepwater Depleted/mature reservoirs Possible application areas:

Engineering module Covers the well construction phase, with particular focus on the main undesirable events: Kick Borehole instability Formation fracturing Differential sticking Features: Quantification of well specific risks Identification of problem areas in the well Comparison of alternative designs and plans Sensitivity analysis on selected parameters RiskSection  Economic module Connected to the engineering module. The profitability measure used is the net present value (NPV). Features: The uncertainty distribution for the total cost of the well Economic basis for directing engineering effort Cost/benefit evaluation of new technology Identification of critical factors & risk reducing measures Compare risks in the well construction phase against gains in the production phase

Connecting the physical models

Technology Monte Carlo simulation to explore all scenarios Addressing all undesirable events simultaneously RF’s borehole temperature and pressure computational technology included

Example of application A B Alternative A: Drill to point A (penetrate 1 pay zone) Alternative B: Drill to point B (penetrate 2 pay zones)

-Overall probabilities -Detailed results -Sensitivity analysis Example of application

Example of application Comparison in terms of NPV

The future: e-risk Risk analyses are often only used in the planning phase As additional data becomes available, the risk picture with respect to selected events can be updated in real-time or near real-time

The future: e-risk Example Failure of critical equipment – drill further? Deviations from plan e.g. casing set 200m higher than planned – change plan? Fracturing of formation – reduction of fracture pressure – change plan?

The future: e-risk