7/27/2019 The Wellbore Quality Scorecard (WQS)

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Publisher Society of Petroleum Engineers Language English

Document ID 98893-MS DOI 10.2118/98893-MS

Content Type Conference Paper

Title The Wellbore Quality Scorecard (WQS)

Authors C.J. Maso n, SPE, BP Exploration, and D.C.-K. Chen, SPE, Halli burton Sperry Drilling Services

Source IADC/SPE Drilling Conference, 21-23 February 2006, Miami, Florida, USA

ISBN 978-1-55563-238-0

Copyright 2006. Society of Petroleum Engineers

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Wellbore quality is a term commonly used i n the drilling comm unity; however its meaning is not cons istently

understood, its context sometim es confused and its value to the industry unknown. For many drilling engineers, a

quality wellbore is mos t often ass ociated with a directionally drilled borehole that is smooth, in-gauge, and has

minim al spiralling. Some of the claimed benefits of such a wellbore include enhanced drilling performance, ease

of running casing, improved logging tool responses and superior cement jobs . To date it has been too difficult or

too complex to directly relate such benefits to wellbore quality in a m eaningful way. This paper describes a new

initiative which has the aim of reducing subjectivity around the quantification of wellbore qual ity. The resulting

scheme is a process whi ch is em bedded in what is called the Wellbore Quality Scorecard (WQS).

The WQS process involves scoring of d rilling, tripping-out and casing running responses for any drilled hole

section. The paper provides background information on issues concerned with wellbore quality and describes the

framework that defines the WQS framework. Risks and complexities ass ociated with the WQS are discussed and

sugges tions made that will improve the robustness of the proposed system. If properly implemented the WQS

has the potential to allow operators to consistently recognise good and poor operational practices and could also

provide an alternative method to assess service provider performance.

Background

It is generally accepted that good wellbore quality positively impacts drilling and completion operations[1-6].

Claimed benefits specifically include: improved hole cleaning efficiency; higher rate of penetration (ROP); reduced

tortuosity; lower torque and drag (T&D) levels; reduced wellbore s piralling; more in-gauge hole; decreased

vibration; fewer tool failures; prolonged bit li fe; improved logging tool responses ; more competent cement jobs ;

easier casing and completion runs. Convincing arguments can be m ade to justify such assertions, however it is

difficult to prove beyond reasonable doubt that good wellbore quality is solely respons ible for such improvements.

More often than not, each drilling team is continuously striving to im prove performance and usually one or more

initiatives are in progress at any one time.

A recent paper[7] discuss ed elem ents of wellbore qual ity that could lead to the construction of a perfect wellbore.

The paper addressed the thorny iss ue of meas uring wellbore quality and reviewed both explicit and im plicit

methods that could be candidates for an indus try approach. The paper concluded that implicit methods offered

the most practicable approach for measuring wellbore quality.

Wellbore Quality

A good s tarting point is to examine potential caus es of well bore quali ty impairment. Most of these arise during the

drilling process but also occur during tripping and casing running operations. The selection and management of

the drilling bottom hole as sem bly (BHA) will prim arily determine whether the wellbore wi ll become tortuous and/or

spiralled. The choice of mud type and the m ud weight program wi ll influence wellbore breakout, the amount of

overbalance and proximity to the fracture gradient. Drilling practices will influence hole cleaning efficiency, the rate

at which the rock is broken and any induced vibration tendencies. Connection and tripping practices will

determine swab and surge pressure cycles. It is cons idered that these could contribute to rock fatigue failure.

Downhole mechanical and equipment failures that result in additional trips can als o jeopardise wellbore quality,

particularly if the hole is time sens itive. Casing and completion running may also impact wellbore quality,

primarily through excess ive surge pressure cycles as each string is run to depth.

File Size 1,119 KB Number of Pages 14

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