PERFORMANCE ENHANCEMENT OF DRILLING FLUIDS USING MOLECULAR ENCAPSULATED PCM

IN HP/HT WELLSPranshu Praleya1, Prakhar Sarkar2

School of Petroleum Technology, Pandit Deendayal Petroleum University, Gandhinagar

pranshu.pbt12@spt.pdpu.ac.in, prakhar.sbt12@spt.pdpu.ac.in

Abstract

With the incessantly rising energy demands from the increasing population worldwide, the situation and the state-of-the-art petroleum and gas technology well herald the time to switch to High Pressure/High Temperature (HP/HT) mode of drilling. Being able to develop and produce from HP/HT wells is a relatively new concept for the upstream industry. This article introduces and discusses the benefits and limitations of a new technology to reduce the temperature of circulating fluids in wellbores. This technology makes use of phase-change materials (PCM), which utilize the latent heat of phase change to absorb the energy transferred to the drilling fluid from the formation or the drilling string.

Keywords- Drilling fluids, Phase Change Materials, HP/HT, Fluids

Introduction

Typically, HP/HT wells were not considered economically viable until the mid- to late-1990s. However, with the recent technological advancements in this field, HP/HT Drilling is no more an abstract concept and has been brought to functional reality in the offshore areas of North Sea, deep waters of the Gulf of Mexico, China and also in the Krishna-Godavari Basin of India. This number is very likely to increase in the coming future.

By definition, HP/HT Wells account for all those wells that have Bottom Hole Temperatures greater than 350˚F (175˚C) and either the maximum anticipated Pore Pressure of any porous formation to be drilled through exceeds a Hydrostatic Gradient of 0.8 psi/ft (EMW of 1.85 SG or 15.4 ppg) or well head shut-in pressures exceed 10 000 psi. A number of formidable challenges are inflicted when it comes to drilling wells with these characteristics. This paper reviews possible solutions of the problems faced by these wells especially in regard with the selection of drilling fluids. Maintaining the thermal stability of the Drilling Fluid so as to maintain its viscosity at the very high imposed temperature and pressure conditions is one of the major challenging problems that this paper seeks to peruse and attempt a viable solution. Loss of fluid viscosity downhole can adversely affect the carrying capacity of the fluid and also the ECD of the system.

The paper recommends the use of certain Molecular Encapsulated Phase Change Material (PCM) as an additive to reduce the temperature of circulating fluids in the wellbore. An unprecedentedly novel technology in this field of oil and gas, PCM is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing

large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid and vice versa; thus. Although Liquid-Gas Transition have a higher Heat of Transition than the Solid-Liquid counterpart, the former is discouraged due to the impracticality of the high volume or high pressure storage of the transformed gas. Molecular Encapsulation Technology allows a very high concentration of PCM within a polymer compound. It is well known to allow drilling and cutting through the material without nay PCM Leakage. PCMs are already in use for a number of applications in different fields of science and engineering. The prospects of their application in Drilling Mud Rheology Modification is covered in the paper.

Conclusion

Phase-change materials have been proposed as an approach to improve the cooling capabilities of drilling fluids for HPHT wells. The maximum benefit of PCMs will depend on the latent heat of the phase change as well as the phase change temperature with respect to the temperature profile of the fluid. In absence of the PCM. There is an optimal phase change temperature that maximizes the decrease of fluid temperature at the bottom of the well.

References

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