PAC-Based Drilling Fluid is the core modified mud additive for modern petroleum drilling operations
PAC can be regarded as an upgraded‑version CMC. It is a water‑soluble cellulose ether featuring superior performance and lower dosage requirement. Compared with conventional CMC, drilling‑grade PAC possesses a higher‑and more evenly‑distributed degree of substitution. It delivers greatly‑improved salt‑resistance, thermal stability and anti‑pollution capacity. PAC maintains stable performance and resists failure even in formations with high‑calcium and high‑magnesium hard‑water conditions
1.PAC‑LV (Low‑Viscosity Polyanionic Cellulose)
Low‑viscosity PAC focuses on powerful fluid‑loss control with slight viscosity‑building effects. It barely affects the overall viscosity and gel strength of drilling‑fluid and avoids excessive mud thickness and overly high pump pressure.
Application scenarios: high‑density drilling, salt‑water or saturated‑salt‑water formations, deep‑well complex formations and high‑solid‑phase mud systems. It has become a dominant additive for high‑pressure complex‑condition drilling nowadays.
2.PAC‑HV (High‑Viscosity Polyanionic Cellulose)
High‑viscosity PAC delivers triple‑functions including thickening, cuttings‑carrying and fluid‑loss reduction. It effectively raises drilling‑fluid viscosity and yield point, improves the suspension and transportation capacity of drill cuttings, and prevents pipe‑sticking caused by settled cuttings.
Application scenarios: shallow freshwater‑based drilling, exploratory drilling in regular formations, working conditions with massive drill cuttings and requirements for improved mud‑suspension performance
Four Core Functions of Polyanionic Cellulose in Drilling Fluid
As a multi‑functional drilling‑fluid additive, PAC is not merely a simple filtrate‑control agent. It comprehensively optimizes mud properties and resolves frequently‑encountered problems during drilling operations.
1.Efficient Filtrate Reduction and Reservoir Protection
After PAC dissolves in water, its high‑molecular anionic chains evenly adsorb onto bentonite particles and rapidly form thin, compact and flexible filter cake on the well‑bore wall. It greatly cuts down API fluid‑loss values, prevents filtrate from invading formations and avoids pore blockage and reservoir damage. Consequently, it preserves reservoir permeability and improves later‑stage production efficiency.
2.Stabilize Wellbore to Prevent Collapse and Hole Shrinkage
For shale layers, loose sand formations and hydration‑prone strata, PAC restrains clay particles from absorbing water, dispersing and hydrating. It locks formation moisture and consolidates well‑bore structures. PAC effectively mitigates common down‑hole troubles such as wellbore collapse, hole shrinkage and rock falling, and drastically lowers risks of complicated down‑hole incidents.
3.Adjust Rheology for Reliable Cuttings‑Carrying and Sticking Prevention
PAC‑HV properly optimizes drilling‑fluid viscosity and gel strength. It ensures favorable flowability during circulation and outstanding suspension performance under static conditions. While drilling, it transports underground cuttings smoothly; when drilling stops, it holds drill cuttings steadily to avoid cuttings accumulation, bit sticking and drill‑pipe sticking, thus improving continuous‑drilling efficiency.
PAC‑LV stabilizes mud rheology without increasing viscosity, which suits high‑pressure and high‑RPM fast‑drilling techniques.
4.Salt and Temperature Resistance for Harsh Working Conditions
Conventional cellulose additives tend to degrade and lose effectiveness under salt‑water, high‑temperature and hard‑water conditions, resulting in sharply increased fluid‑loss. By contrast, drilling‑grade PAC features prominent resistance to salt, calcium, high temperature and contamination. It is compatible with freshwater, seawater and saturated‑salt‑water drilling‑fluid systems and maintains stable performance at elevated temperatures in medium‑depth and deep wells. It is well‑suited for drilling projects in coastal areas, saline‑alkali lands and complex geological zones.
