EZFLOW Non-Gel Breaking Water-based Drill-in Fluid

Overview：

EZFLOW is a weak-gel drill-in fluid system, which can form a thin, tough and dense filter cake near the borehole wall during drilling. The filter cake can be lifted and automatically flowed back after drilling, minimizing the potential impairment to the reservoir. It offers the benefits of lower cost and technical superiority. It has been successfully applied on many projects, both locally and internationally.

Applicability：

Temperature: ~ 170℃；Density: 1.05~1.70 g/cm3；Low-pressure/depleted reservoirs；Horizontal well reservoir section；Open hole completion

Characteristics：

Excellent hole cleaning capacity；High viscosity at low shear rate；Low reservoir impairment；Low flowback pressure without acid treatment；Natural materials, easily degradable.

EZFLOW gel free water-based drilling fluid system case

Operation background:

A gas field in the west of the South China Sea is deeply buried, with low formation fracture pressure and high shale content. During the drilling of horizontal wells, mud making of mudstone leads to the increase of drilling fluid viscosity and shear force, and the increase of circulating equivalent density (ECD) leads to frequent formation leakage problems. The target layer is a low porosity and low permeability reservoir, mainly composed of gray mudstone mixed with fine sandstone and argillaceous siltstone, belonging to the normal temperature and pressure system, and the bottom hole temperature is up to 169 ℃.

Challenges encountered:

The target gas field has the characteristics of high temperature burial depth, large water vertical ratio, low porosity and low permeability, complex trajectory, long open hole section, etc. The drilling fluid of the reservoir needs to have long-term temperature resistance stability, good anti-wear and drag reduction effect in long horizontal section, etc. Especially for the low porosity and low permeability reservoir section, the use of direct flowback operation mode has put forward strict requirements to ensure good reservoir protection effect.

Solution:

EZFLOW gel free water-based drilling fluid system is used as the basic system to improve the inhibition performance of the drilling fluid and take into account the downhole ECD added value. In combination with the reservoir sensitivity characteristics, the particle size grading temporary plugging agent is selected to reduce the invasion damage of the solid and liquid phases, and the matching high-temperature waterproof locking agent reduces the surface tension to improve the porous seepage capacity, so as to ensure a good reservoir protection effect of the system.

Job results

The system uses high temperature resistant and stable flow regulator and fluid loss reducer, and the performance is stable under long-term aging at 169 ℃; The horizontal section of the target gas field is 1040m long. The friction and drag reduction effect of the system is obvious. The actual drilling torque is significantly reduced compared with the prediction, and the ECD added value is 0.07g/cm3; The operation wells were put into production by direct flowback, and the production reached the production allocation requirements, showing good reservoir protection effect of high temperature and low permeability reservoir operation, laying a foundation for the smooth operation of deep wells in long open hole horizontal section.