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Research Papers: Petroleum Wells-Drilling/Production/Construction

# Analysis of Postbuckling Drillstring Vibrations in Rotary Drilling of Extended-Reach Wells

[+] Author and Article Information

Aquatic Co., a Weatherford Co., Bd. 1, 4/6 3rd Monetchikovsky Pereulok, Moscow 115054, Russiavadim.tikhonov@eu.weatherford.com

Alexander I. Safronov

Aquatic Co., a Weatherford Co., Bd. 1, 4/6 3rd Monetchikovsky Pereulok, Moscow 115054, Russiasafronov@100km.ru

J. Energy Resour. Technol 133(4), 043102 (Dec 07, 2011) (8 pages) doi:10.1115/1.4005241 History: Received March 14, 2010; Revised September 09, 2011; Accepted September 26, 2011; Published December 07, 2011; Online December 07, 2011

## Abstract

One of the most serious concerns of extended-reach drilling is the dynamic behavior of the drillstring and the cleaning of well. Good cleaning requires an increased angular velocity. This paper presents a 3D nonlinear dynamic model of drillstring in a wellbore of 3D profile. The model suggests possible contact/lift-off of drill pipes with/from the wellbore wall. The interaction of lateral, torsional, and axial vibrations is taken into account. The relation between the normal component of contact force and the deformation of the wellbore wall is taken as quadratic-elastic. The friction force is described based on a hysteretic dynamic model. The friction force model also takes into account, the transition from a sliding to whirling. The equations of drillstring dynamics are solved numerically using the method of lines. The DYNTUB software is developed to analyze the drillstring time-varying processes under different loads. The program is used to study the effects of angular velocity, compression load, torque, friction factor, well profile, and availability of connectors on the drillstring dynamic behavior. From the study follows the key conclusions: (1) The friction factor has a considerable effect on the drillstring rotational behavior in the wellbore; (2) no whirling of drillstring at real value of rolling friction factor in a horizontal well in the discussed examples could be seen at all; (3) when whirling takes place, the contact force shows a dramatic times increase; and (4) snaking can be seen in any wells at moderate compressive load and angular velocity.

## Figures

Figure 1

Quadratic-elastic model of normal contact force

Figure 2

Hysteretic model of friction force

Figure 3

Coordinate systems

Figure 4

Scheme of interaction of drillstring and wellbore wall

Figure 5

Scheme of boundary conditions for drillstring

Figure 15

Distribution of contact force on length for drillstring with connectors in curved wellbore at maximum compressive load equal 250 kN, rolling friction factor 0.3 and distance between connectors 5.6 m

, α(0) = 45 deg, α′ = −1/150 m−1 ;
, α(0) = 90 deg, α′ = 1/150 1/m

Figure 14

Transient processes of contact force in middle point for drillstring with connectors in curved wellbore at surface load equal 250 kN, rolling friction factor 0.3 and distance between connectors 5.6 m

, α(0) = 45 deg, α′ = −1/150 1/m;
, α(0) = 90 deg, α′ = 1/150 1/m

Figure 13

Transient processes of contact force (a) and rotation angle (b) in middle point for drillstring with connectors at rolling friction factor equal 0.3 and distance between connectors 5.6 m

, steel pipes, inclination = 90 deg, Qg  = 400 kN;
, aluminum pipes, inclination = 45 deg, Qg  = 250 kN;
, steel pipes, inclination = 45 deg, Qg  = 250 kN. (Note The program uses the algorithm in which count of rotation angle at the instant of the first contact of a drill pipe with a wellbore wall each time begins with value −90 deg < ϕ(s) ≤ 270 deg (see blue curve). At no-contact rotation angle is not defined.)

Figure 12

Distribution of contact force on length for drillstring without connectors in inclined wellbore α = 45 deg and at rolling friction factor equal 0.25

, Qg  = 100 kN;
, Qg  = 250 kN

Figure 11

Transient processes of contact force (a) and rotation angle (b) in middle point for drillstring without connectors in inclined wellbore α = 45 deg and at rolling friction factor equal 0.25

, Qg  = 100 kN;
, Qg  = 250 kN

Figure 10

Distribution of contact force on length for drillstring with connectors at rolling friction factor equal 0.2, sliding friction factor = 0.38

, inclination = 45 deg, ΔL = 11.2 m;
, inclination = 10 deg, ΔL = 5.6 m;
, inclination = 45 deg, ΔL = 5.6 m

Figure 9

Transient processes of contact force (a) and rotation angle (b) in middle point for drillstring with connectors at rolling friction factor equal 0.2

, inclination = 45 deg, ΔL = 11.2 m;
, inclination = 10 deg, ΔL = 5.6 m;
, inclination = 45 deg, ΔL = 5.6 m, sliding friction factor = 0.38; ——, inclination = 45 deg, ΔL = 11.2 m, sliding friction factor = 0.6

Figure 8

Transient process of contact force in midpoint of nonrotated drillstring in inclined wellbore, α = 45 deg, drillstring without connectors

; drillstring with connectors
, ΔL = 5.6 m

Figure 7

Transient process of contact force in midpoint of nonrotated drillstring in horizontal wellbore drillstring without connectors

; drillstring with connectors:
, ΔL = 11.2 m,
, ΔL = 5.6 m

Figure 6

5 in. Compressive service drill pipe

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