Executive Summary
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Well intervention planning is a systematic, risk-based process that transforms a defined objective into a safe, efficient, and executable field procedure. It is not merely a checklist but a cycle of data acquisition, engineering analysis, and iterative refinement.

The primary goal is to develop a robust program that safely and efficiently achieves the intervention objective while minimizing risk to personnel, the environment, and the asset.

The Digital Twin Philosophy

The ultimate goal is to create a "digital twin" of the intervention operation through modeling, allowing the team to predict outcomes, identify failure modes, and prepare contingencies before committing costly equipment and personnel to the wellsite.

The choice of conveyance—Slickline, Coiled Tubing (CT), or Electric Line (E-line)—is a pivotal decision that dictates the entire engineering scope, risk profile, and potential success of the operation.

1 Intervention Scoping, Justification & Concept Selection
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This initial phase defines the "why" and establishes the high-level feasibility and business case for the operation.

Flow of Steps

1. Problem Identification & Opportunity Analysis

  • Trigger: Production decline, well integrity issue (e.g., SCSSV failure), reservoir management requirement (e.g., PLT), or new technology trial.
  • Action: Quantify the problem with specific metrics.
Example: Instead of "production dropped," use: "Oil production has declined from 1,500 bopd to 800 bopd over 60 days, with a corresponding increase in water cut from 10% to 40%."

2. Define Clear, Measurable Objectives

Use the SMART (Specific, Measurable, Achievable, Relevant, Time-bound) framework.

Poor Example: "Find out why the well is watering out."

SMART Example: "Acquire a production log (PLT) across zones X, Y, and Z (4,500-5,200 ft MD) to identify water entry points with a flow rate accuracy of +/- 10%, enabling a targeted water shut-off within the next quarter."

3. Conceptual Method Screening & High-Level Feasibility

A multi-disciplinary team (Production Engineer, Intervention Engineer, Reservoir Engineer) performs a high-level screening.

Key Considerations:

  • Well Geometry: Is the well highly deviated or horizontal? (Favors CT/E-line)
  • Pressure Control: What are the expected surface pressures? (High pressure may favor slickline or require more robust CT/E-line pressure control equipment)
  • Objective Complexity: Is it a simple mechanical set (Slickline) or does it require real-time data or pumping (CT/E-line)?
  • Logistics & Cost: What is the available budget and platform/rig space?

Data Required to be Added/Inputted for the Program:

Intervention Justification Document (IJD): A formal document containing the problem statement, SMART objectives, and preliminary cost-benefit analysis.
Conceptual Feasibility Memo: A brief technical report outlining the pros and cons of Slickline, CT, and E-line against the specific objective, recommending one or two methods for detailed engineering.
2 Comprehensive Data Gathering & Well History Analysis
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This is the foundational data acquisition phase. The quality of the entire intervention program is entirely dependent on the quality of the data gathered here.

Flow of Steps

  1. Establish a "Master Data File": Create a single, controlled repository for all well-related information.
  2. Collect Static Well Data: The unchanging physical characteristics of the well.
  3. Collect Dynamic Well Data: The current state and historical performance of the well.
  4. Perform a "Digital Wellbore Review": Virtually run the planned tools through the wellbore schematic to identify potential restrictions or interference points.

Data Required: The Master Data File

1. Well Trajectory & Geometry

Data: Directional survey data (MD, TVD, Inclination, Azimuth) for the open hole, cased hole, and tubing.
Usage: Critical for CT Force/Torque Modeling to predict reach, calculate lock-up depth, and simulate buckling. Essential for E-line/Slickline to predict tool drag and ensure tools can reach TD.

2. Completion Hardware & Strings

Tubing String: Make-up, size, weight, grade, thread type, ID, drift ID, special connections, upset lengths. A detailed tally of all joints.
Casing/Liner String: Same as tubing data.
Completion Schematic: The official, as-built drawing. Must be verified against the final well report.
Profile Nipples: Type (e.g., Select-F, F, R), size, top depth, and bottom depth for all profiles (X, Y, Z, etc.).
Packers: Type, setting depth, setting mechanism (wireline-set, hydraulically-set), bore ID.
Subsurface Safety Valves (SCSSV): Type (flapper vs. sleeve), setting depth, control line pressure (operating and test), fail-safe position (open/close).
Gas Lift Equipment: Mandrel types (concentric vs. side-pocket), valve depths and ratings.
Usage: Determines toolstring compatibility (clearance), depth correlation points (CCL on collars, profiles), and potential obstruction locations.

3. Reservoir & Fluid Properties

Pressures: Current reservoir pressure, static bottomhole pressure (SBHP), flowing bottomhole pressure (FBHP).
Temperatures: Static bottomhole temperature (SBHT) and expected flowing temperature (FBHT).
Fluid Properties: PVT analysis – oil, water, gas densities (SG), viscosities, GOR (Gas-Oil Ratio). Water chemistry (chlorides, scaling potential). H₂S and CO₂ concentrations (mol%).
Usage:
  • P/T: Essential for selecting tool and equipment ratings (O-rings, electronics). Affects fluid viscosity for hydraulic modeling.
  • Fluid Densities: Used for hydrostatic pressure calculations, well control scenarios, and buoyancy calculations in CT modeling.
  • H₂S/CO₂: Drives material selection (requiring sour service equipment like 75K/SSSS or Duplex steels) and dictates H₂S safety levels (requires personal H₂S monitors, breathing apparatus).

4. Well History & Performance

Production/Injection History: Plots of rates (oil, gas, water), pressures (tubing head, casing head), and choke settings.
Previous Intervention Reports: Detailed reports for all past interventions. Pay close attention to tools run, successes/failures, "stuck pipe" or "lost in hole" incidents, and deviations from the original program.
Usage: Provides empirical evidence of what has worked or failed in this specific wellbore. Helps identify recurring problems (e.g., a known tight spot at 8,500 ft) that must be planned for.
3 Detailed Engineering, Program Development & Risk Mitigation
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This is where the data is transformed into a predictive model and a robust, step-by-step operational procedure.

Flow of Steps

  1. Finalize Conveyance Method & BHA Design
  2. Perform Predictive Simulations & Modeling
  3. Draft the Detailed Intervention Program
  4. Conduct a Formal Risk Assessment (HAZOP/HAZID)
  5. Develop Detailed Contingency & "Get-Out-of-Jail" Plans

Conveyance Method Comparison

Feature Slickline Coiled Tubing (CT) Electric Line (E-line)
Primary Function Simple mechanical manipulation (setting/retrieving plugs, valves, gauges) Mechanical manipulation, pumping/circulation, logging, milling, cleanouts High-resolution data acquisition, selective perforation, mechanical manipulation
Conveyance Simple solid wire. No real-time surface readout Continuous steel pipe. Can pump fluids. Can have real-time data (with e-coil) Armored cable with electrical conductors. Provides real-time data
Force Low axial force High axial force. Can push through high doglegs and debris Low axial force (similar to slickline)
Data None (unless memory tools are used) Can have real-time data (CT-Head T/P, CCL) and downhole memory tools Real-time, high-bandwidth data (CCL, GR, CBL, PLT, etc.)

Predictive Simulations: The "Digital Twin"

CT Force & Torque Analysis: Models mechanical forces on the CT string. Predicts the lock-up depth (where the CT can no longer be pushed), helical buckling, and the maximum pull force required to retrieve the string.
CT Hydraulics Simulation: Models fluid flow to predict surface pump pressure, annular velocity (for effective cleanouts), and ECD (Equivalent Circulating Density) to avoid fracturing the formation.
Perforating Ballistics & Shock Modeling: Predicts the pressure wave, dynamic shock loads, and wellbore temperature changes from detonation, ensuring downhole equipment can withstand the event.
Transient Multiphase Flow Simulation: For complex cleanouts in live wells, simulates gas, oil, water, and solids interactions to predict slugging and pressure fluctuations.
Wireline Stretch & Fatigue Modeling: Calculates wire elongation for accurate depth correction and tracks cumulative damage to determine when the wire should be retired.

Risk Assessment (HAZOP)

HAZOP (Hazard and Operability Study) is a structured brainstorming session where the team uses guidewords (e.g., No, More, Less, Reverse) to identify potential deviations from the design intent.

HAZOP Outputs:

  • Risk Register: A table detailing each hazard, its cause, consequences, likelihood, and severity.
  • Mitigation Measures: Specific actions to reduce the risk to an As Low As Reasonably Practicable (ALARP) level.

Contingency Planning

Detailed, standalone plans for worst-case scenarios:

  • Stuck Pipe/CT Plan: What steps will be taken? What fishing tools are required?
  • Well Control Plan: What are the kill fluid densities and volumes? What is the kill method (circulation vs. bullheading)?
  • Equipment Failure Plan: What is the backup if a primary tool fails on location?
4 Human Factors, Decision-Making & Crew Resource Management
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A technically perfect program is useless if it's not executed correctly by a competent, cohesive team. This phase focuses on the human element.

Flow of Steps

  1. Establish a "One-Team" Culture: Break down silos between the operator company and the service company.
  2. Implement Crew Resource Management (CRM): Adopt principles from aviation to improve communication and decision-making.
  3. Define a Clear Decision-Making & Authority Matrix: Empower the team to stop the job if necessary.

CRM Principles & Communication Protocols

Pre-Job CRM Briefing: A structured briefing where every person is encouraged to speak up about concerns.
"Time-Out for Safety" Authority: A formal policy that gives any crew member the authority and obligation to call a "stop work" if they feel something is unsafe.
Closed-Loop Communication: A protocol for confirming critical instructions by repeating them back.

Decision Gates & Go/No-Go Criteria

A set of predefined criteria that must be met before proceeding to the next major phase of the operation. This structured approach prevents "press-on-itis" and ensures operations only proceed when all conditions are safe.

5 Pre-Execution, Logistics & Field Execution
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This phase is about mobilizing the right people and equipment to the location and executing the plan safely.

Flow of Steps

  1. Final Equipment Check & Certification: Verify all equipment matches the program list and has valid test certificates.
  2. Personnel Verification: Confirm all crew members have valid, role-specific certifications (e.g., IWCF Well Control).
  3. Pre-Job Safety & Planning Meeting (Toolbox Talk): The entire crew on location walks through the program, the HAZOP findings, and their individual roles.
  4. Execution & Real-Time Monitoring: The supervisor executes the program while continuously comparing actual vs. predicted parameters (e.g., surface weight vs. CT model, pump pressure vs. hydraulic model).
  5. Documentation: The Supervisor accurately logs all times, depths, weights, pressures, and any deviations from the plan.

Required Documentation

  • Equipment Certification Dossiers: Copies of all pressure test certificates, calibration certs, and inspection reports.
  • Crew Competency Matrix: A signed-off document verifying personnel qualifications.
  • Signed-Off JSA/TBM Records: Proof that the pre-job safety meeting was held and attended.
  • Daily Morning Reports: Documents containing the actual data from the job (weights, depths, pressures, times, issues encountered).
6 Post-Job Analysis, Knowledge Management & Continuous Improvement
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This is the most important phase for long-term asset management. The goal is to ensure that lessons learned are captured, analyzed, and disseminated to prevent future failures and repeat successes.

Flow of Steps

  1. Conduct a Formal Post-Job Review (PJR)
  2. Perform a "Root Cause Analysis" (RCA) for any Deviations
  3. Update the "Living" Well File and Knowledge Base

Critical Outputs

Post-Job Review (PJR) Report: A structured report that answers: What went well? What did not go according to plan? What can we do differently next time?
Root Cause Analysis (RCA): An investigation that goes beyond the immediate cause to find the systemic failures that led to the event.
Updated "Digital Twin" and Knowledge Base:
  • Well File Update: The Final Job Report, PJR, and RCA are permanently attached to the well's digital file.
  • Calibration of Simulators: The actual job data is used to "calibrate" the engineering models, making the next simulation more accurate.
  • Lessons Learned Database: Actionable items from the PJR are entered into a searchable, company-wide database. This transforms individual experiences into institutional knowledge.

The Continuous Improvement Cycle

By integrating these phases, the well intervention planning process evolves from a simple procedural task into a sophisticated, closed-loop system of continuous learning and improvement, ultimately leading to safer, more efficient, and more successful outcomes.