How do you manage multiphase flow assurance?

1 Flow regimes

Multiphase flow can exhibit different patterns or regimes depending on the relative velocities, densities, and viscosities of the fluid phases (gas, liquid, and solid). Some common flow regimes are bubble, slug, churn, annular, and stratified flow. Each regime has its own characteristics, advantages, and drawbacks for multiphase flow assurance. For example, slug flow can cause severe pressure fluctuations, erosion, and corrosion, while annular flow can enhance heat transfer and reduce hydrate formation.

2 Flow models

To predict and optimize the multiphase flow behavior, engineers use various mathematical models and numerical methods that account for the fluid properties, flow geometry, and boundary conditions. Some of the most widely used models are mechanistic models, empirical correlations, and computational fluid dynamics (CFD). Mechanistic models are based on physical principles and conservation laws, while empirical correlations are derived from experimental data and curve fitting. CFD is a powerful tool that can simulate the detailed flow dynamics and interactions using discretized equations and numerical solvers.

3 Flow assurance issues

Multiphase flow assurance involves addressing a range of technical and operational issues that can impact the performance, reliability, and safety of oil and gas systems. Hydrate formation, wax deposition, asphaltene precipitation, scale formation, corrosion, and erosion are among the major issues that must be addressed. Hydrates are ice-like crystals that form when water and natural gas are exposed to low temperatures and high pressures, which can block flow lines and equipment. Wax is a solid or semi-solid substance that precipitates from crude oil when the temperature falls below the wax appearance temperature (WAT). Asphaltenes are heavy hydrocarbon molecules that can precipitate from crude oil when the pressure drops below the asphaltene onset pressure (AOP). Scale is a mineral deposit that forms when water-soluble salts are precipitated due to changes in pressure, temperature, pH, or composition. Corrosion is the deterioration of metal materials due to chemical or electrochemical reactions with the environment. Erosion is the mechanical wear of metal surfaces due to the impact of solid particles or liquid droplets in the flow. All of these issues can reduce flow area, increase pressure drop, cause leaks and failures, and reduce the life span of pipes and equipment.

4 Flow assurance solutions

To overcome the multiphase flow assurance issues, engineers apply various solutions that can be classified into three categories: prevention, mitigation, and remediation. Prevention solutions aim to avoid or minimize the occurrence of the issues by modifying the fluid properties, flow conditions, or system design. For example, adding inhibitors, stabilizers, or antifreeze agents can prevent hydrate, wax, or asphaltene formation. Mitigation solutions aim to reduce or control the impact of the issues by adjusting the operational parameters, applying external forces, or installing additional equipment. For example, increasing the temperature, injecting chemicals, or using pigging devices can mitigate wax, scale, or corrosion problems. Remediation solutions aim to restore or improve the flow performance by removing or dissolving the existing deposits, blockages, or damages. For example, using solvents, acids, or mechanical tools can remediate hydrate, asphaltene, or scale issues.

5 Flow assurance strategies

To implement multiphase flow assurance solutions effectively and efficiently, engineers need to adopt strategies that consider technical, economic, and environmental factors. For instance, risk assessment is important for identifying and evaluating potential hazards and consequences of the multiphase flow assurance issues. Monitoring and control processes measure, observe, and regulate the multiphase flow parameters and performance. Additionally, optimization and integration processes maximize the efficiency, profitability, and sustainability of the solutions. Ultimately, understanding the fundamentals, issues, solutions, and strategies of multiphase flow assurance can enhance skills and knowledge as a petroleum engineer while contributing to the success of the oil and gas industry.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?