JNTU B.Tech IV PETROLEUM RESERVOIR STIMULATION Previous Question Paper (February/March - 2022 - R18)

Candidate selection is the systematic process of identifying wells that are underperforming compared to their potential, followed by a diagnostic evaluation to determine if the cause is mechanical or reservoir-related. The process follows these key steps:

1. Performance Comparison: Compare actual well performance against theoretical inflow performance relationship (IPR) curves or offset well data. Wells with a significant deviation between actual and potential production are flagged as candidates.
2. Data Gathering: Compile historical production data, pressure transient analysis, well logs, and completion reports to identify trends in productivity index (PI) decline.
3. Mechanical Integrity Evaluation: Inspect the wellbore for mechanical issues such as scale buildup, paraffin deposition, sand production, or casing/tubing leaks. This often involves running a production log (PLT) or a camera survey to identify specific zones of water or gas breakthrough.
4. Damage Identification: Distinguish between skin damage (near-wellbore impairment) and reservoir depletion. If the skin factor is high, the well is a strong candidate for stimulation (acidizing or fracturing).
5. Economic Screening: Evaluate the cost of the proposed stimulation treatment against the expected incremental production to ensure the project meets the required return on investment.

The pertinent rock properties required for reservoir stimulation design include porosity, permeability, mineralogy, and geomechanical characteristics. These are measured through the following methods:

• Porosity: Defines the storage capacity of the rock. It is measured in the laboratory using core analysis (helium porosimetry) or in-situ via neutron-density logs.
• Permeability: Determines the fluid flow capacity. It is measured via core flow tests in the laboratory or through pressure transient analysis (well testing) to obtain the effective permeability of the reservoir.
• Mineralogy: Essential for selecting stimulation fluids, particularly for acidizing. X-ray diffraction (XRD) and thin-section petrography are used to identify reactive minerals like carbonates or clays that could cause formation damage.
• Geomechanical Properties: Young's modulus, Poisson's ratio, and in-situ stress magnitude are critical for hydraulic fracturing design. These are measured using triaxial compression tests on core samples or estimated from sonic logs (acoustic velocity measurements).