• Worldwide demand for energy continues to increase at rates never before seen.

• The demand is widespread geographically and impacts all energy sources.

• The Hydrocarbon demand is driving the oil and gas industry to explore new or under-explored areas.

• As the search for petroleum becomes more extreme in terms of depths, pressures, and temperatures, innovative technologies have been formulated for High-Pressure, High-Temperature (HPHT) drilling.

HPHT FLUID SYSTEMS

• Introduction.• Challenges faced by HPHT Drilling fluids.• New technologies in HPHT Drilling fluids.• Preventive measures of Barite Sagging.

• HPHT wells are defined as wells that have an initial reservoir pressure greater than 10k psi(69 MPa) or reservoir temperature greater than 300 oF(149oC).

• When dealing with High Pressure and Temperature everything becomes more challenging due to the natural conditions taking place within the wellbore and reservoir.

HPHT Drilling Fluid Challenges

• Require a higher density fluid which typically requires high solids loading.

• High solids loading, the resulting higher pressures, combined with the competency of rock at depth, lead to low penetration rates, extending time on location and added drilling costs.

• Thermal degradation of polymers.

• Under high temperatures , high pressures it becomes extremely difficult to control the gelation.

HPHT DRILLING FLUID CHALLENGES

Plastic viscosity As low as reasonably possible to minimize ECD.

Yield stress and gels Sufficient to prevent sag, but not as high as to cause gelation, or high surge and swab pressures.

HPHT fluid loss As low as reasonably possible to prevent formation damage and risk of differential sticking.

HPHT Rheology Predictable in order to control sag, gelation &ECD.

Stability to contaminants

Stable in the presence of gas, brine and cement.

Stability to aging Properties do not change overtime under either static or dynamic conditions.

Weighing Must be able to weighed up rapidly if a kick is taken.

Gas solubility Needed for accurate kick detection & modeling.

• Typically, oil-base drilling fluids are preferred over their water-base counterparts in applications where bottom hole temperatures can approach 260° C (500° F) with shut-in pressures to 25,000 psi, thereby requiring densities as high as 19 lb/gal.

• More areas are prohibiting the discharge of oil-base fluids and cuttings, which increases waste management costs and potential liabilities.

• CHROME FREE WBM.• UNDER BALANCED DRILLING.• FORMATE BRINE SOLUTIONS.

CHROME FREE WBM

A newly designed, chrome-free high density water-base drilling fluid:

• Low molecular-weight anionic polymers.• Synthetic polymers.• The high-molecular weight vinyl sulfonate

copolymers.• Synthetic seawater.• Divalent metal lignosulfonate.

• Invert emulsion fluids have been used for drilling HP/HT wells, and the technology is adequate for temperatures up to 500°F.

CONVENTIONAL OVER-BALANCED DRILLING

UNDER BALANCED DRILLING

OVER BALANCED DRILLING

BENEFITS OF UNDER BALANCED DRILLING

• Prevention formation damage.

• Increase well productivity.

• Limit drilling fluid loss.

• Increase rate of penetration.

FORMATE BRINE

• Cesium formate brine has been used in numerous challenging HPHT wells .

• Cesium formate brine is a high-density, low-viscosity clear fluid that provides the basis for a non-damaging, hydraulically efficient HPHT reservoir drilling fluid.

VISCOSITY MEASUREMENTS

CHANDLER 7600 VISCOMETER

BARITE SAGGING

BARITE SAGGING

• The significant density variations during some operations that require the mud to remain static for an extended period of time.

• Static sag, is caused when circulation is stopped for an extended period of time and the weighting agents begin to settle under the influence of gravity.

BARITE SAGGING

METHODS FOR PREVENTING BARITE SAGGING

• The ways involve replacing barite by other weighted materials such as ilmenite , haematite, or manganese tetra oxide.

• The lower the Equivalent Circulating Density, the higher the rate of drilling operation as well as the lower pressure losses, especially in mud pumps.

• A new water-based mud formulation is introduced that uses polyanionic cellulose and xanthan gum as viscosifiers.

REFERENCES

• Article adapted from AADE Paper No. 10-DF-HO-37, "Environmentally Responsible Water-based Drilling Fluid for HPHT Applications," presented at the 2010 AADE Fluids Conference and Exhibition.

• Article based on a paper presented at the IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition, Bangkok, Thailand.

• www.cabotspecialityfluids.com• www.spe.onepetro.com

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