API RP 13C-2023
Recommended Practice on Drilling-fluid Processing Systems Evaluation
- Standard No.
- API RP 13C-2023
- Release Date
- 2023
- Published By
- American Petroleum Institute (API) US / API
- Introduction
Standard Background and Technical Evolution
Since its release, API RP 13C has undergone six revisions. The sixth edition (2023) places new emphasis on the systematic performance evaluation methods for drilling fluid treatment systems and introduces standardized measurement procedures for vibrating screen mesh conductivity, D100 separation particle size, and non-blank area, filling a gap in the industry regarding solid control equipment comparison. Technical evolution is reflected in the shift from single equipment evaluation to system-level efficiency (ηDSR) and waste volume optimization.
Core Indicators for System Performance Evaluation
System performance evaluation is based on two parameters: solid removal efficiency (ηDSR) and the drilling fluid-to-cuttings ratio (RDF-DS). ηDSR reflects the equipment's ability to remove cuttings, while RDF-DS measures drilling fluid loss. These two parameters have a mutually exclusive relationship, and the optimal operating point requires balancing them.
Indicator Definition Optimization Direction ηDSR Percentage of cuttings volume discarded by the equipment relative to the total cuttings volume Increasing to above 85% significantly reduces dilution requirements RDF-DS Volume ratio of drilling fluid to dry cuttings in discarded wet cuttings Below 2:1 indicates good drilling fluid retention Equipment Efficiency Testing (Capture Analysis)
For centrifuges and hydrocyclones, Capture analysis is used to evaluate single-unit efficiency. By sampling feed, overflow, and underflow slurries, the capture fraction of suspended solids is calculated. For example, when the underflow solid mass fraction w3 is higher than the feed w1, it indicates effective separation. In a practical case, an oilfield used a centrifuge to treat weighted drilling fluid, achieving a Capture rate of over 85% and reducing drilling fluid dilution volume.
Standardization of Vibrating Screen Mesh Characteristics
Key parameters for the mesh include conductivity (kD/mm), D100 separation particle size (μm), and non-blank area (m²). Conductivity reflects fluid permeability, D100 represents the equivalent mesh aperture size, and non-blank area determines the effective processing area. Together, these three factors determine mesh performance. For instance, API 170 mesh has a D100 range of 82.5-98μm; higher conductivity results in greater throughput for the same mesh number.
Implementation Recommendations and Optimization Strategies
1. Monitor ηDSR and RDF-DS daily and adjust the vibrating screen mesh mesh size based on data. 2. When using centrifuges with weighted drilling fluid, discard the light phase (containing colloidal particles) to maintain rheology. 3. Ensure equipment installation sequence: vibrating screen → desander → desilter → centrifuge, with each device drawing from separate compartments. 4. Regularly calibrate instruments and test mesh conductivity and separation efficiency using API RP 13C methods.
