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Research Papers: Petroleum Engineering

Thermoporoelastic Modeling of Time-Dependent Wellbore Strengthening and Casing Smear

[+] Author and Article Information
Raj Kiran

Mewbourne School of Petroleum
and Geological Engineering,
University of Oklahoma,
Norman, OK 73019

Saeed Salehi

Assistant Professor
Mewbourne School of Petroleum
and Geological Engineering,
University of Oklahoma,
Norman, OK 73019
e-mail: saeads@gmail.com

1Corresponding author.

Contributed by the Petroleum Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received February 15, 2016; final manuscript received April 22, 2016; published online July 25, 2016. Editor: Hameed Metghalchi.

J. Energy Resour. Technol 139(2), 022903 (Jul 25, 2016) (7 pages) Paper No: JERT-16-1092; doi: 10.1115/1.4033591 History: Received February 15, 2016; Revised April 22, 2016

One of the most critical aspects in the drilling operation is to reduce the nonproductive time and to avoid the borehole instability issues such as kicks, blow outs, lost circulation, stuck pipe, and breakouts. To investigate these problems, one has to understand the formation properties, fluid hydraulics, and the basic mechanics behind drilling a well. In the previous research on this field, the factors were widely discussed and results obtained were related to the formation properties. However, while considering the stresses in the wellbore, the mechanical factors such as the RPM and contact of casing at different positions in wellbore have usually been neglected. In furtherance to this study, the importance of thermal condition, fluid loss, and filter cake formation study cannot be out ruled. This work includes a new insight toward understanding the stress redistribution due to pipe contact by the wellbore and smear mechanism. Additionally, it presents the numerical analysis of influence of casing contact and downhole thermal conditions using the finite-element analysis. The classical equations used to obtain the wellbore stresses include very few parameters such as the far-field stresses, pore pressure, and wellbore geometry. They do not consider the influence of casing contact while drilling, mud-cake permeability, and elastic and inelastic properties of the formation. To take into account the effects of these parameters, finite-element analysis is carried out considering the above-mentioned parameters in various scenarios. The main objective of these simulations is to investigate the hypothesis of the increase in hoop stress considering casing contact with regard to formation stresses orientation. The study of different cases shows the variation of a few hundred psi of hoop stress. However, the thermal effect on the near-wellbore stress regions can be important for drilling in deep water and other complex drilling environments. To see the thermal effect, this study develops a thermoporoelastic model. It is found that there is decrease in radial stress and hoop stress in near-wellbore region with time. This reduction will have a considerable impact on fracture initiation pressure in the near-wellbore region. Also, the smearing effect will be influenced by stress changes due to change in temperature.

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References

Figures

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Fig. 1

Finite-element analysis poroelastic model including the boundary conditions

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Fig. 3

Variation of radial stress and hoop stress with Young's modulus

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Fig. 4

Variation of radial stress and hoop stress with Poisson's ratio

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Fig. 5

Hoop stress around the wellbore with varying RPM when contact force is applied along maximum horizontal stress orientation

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Fig. 6

Hoop stress around wellbore with varying RPM when contact force is applied along minimum horizontal stress orientation

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Fig. 7

Hoop stresses around wellbore with varying annulus-to-hole (A/H) ratio when contact force is applied along minimum horizontal stress orientation

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Fig. 8

Hoop stresses around the wellbore with varying annulus-to-hole (AHR) ratio when contact force is applied along maximum horizontal stress orientation

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Fig. 9

Sandstone slabs used in the experiments with a range of permeabilities

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Fig. 10

Variation in hoop stress in 1110 mD formation with time

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Fig. 11

Variation in hoop stress for different formations with time

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Fig. 12

Hoop stress around the borehole in field case

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