You are here:

Geology/well site question

Advertisement


Question
sir,
   1:how we pick or set or judge the casing point on the biases on pressure's confused in these tell me please.??
2: what is drilling exponent tell me in easy wording ?
3:what is difference between leak off test & formation integrity test in easy word?
regard
waqar
internee geologist

Answer
Dear Waqar Ahmed,

Thanks for sending me your question.

Casing is very important for any drilling well as it provides the safe pathway for bit to drill new formation. Therefore, it's essential that seat of the casing should be anchored in a formation which is strong enough to hold the pressure of casing and circulation pressure while cementing. For example foundation of any house are set on the cohesive base which can hold the weight of the building without failure, ideally on top of sandstone or limestone. Same principal can be applied for the well casing. However, if ideal rock surface is not available or operational urgency demands an early casing then casing shoe can be set in any relatively stronger rocks.

D exponent is the extrapolation of drilling parameters to determine any deviation from the normal pressure trend line. The objective of this exercise is to observe over pressure situation while drilling to avoid major accident such as high pressure kick or blow out which could be disastrous and fatal. Drilling parametrs are used  for D exponent are, rate of penetration (ROP) Weight on bit (WOB), Rotary speed (RPM) and bit size.
The general formula of D exponent is as follows;

d = log (R 60N) log (12W 1000D)Where; R = penetration rate in feet per hour, d = exponent in drilling equation, dimensionless, N = rotary speed in rpm , W = weight on bit in kilo pound
D = bit size in inch

Any abnormal pressure change will increase or decrease calculated D exponent from the normal trend line and action to be taken to control the potential problem.

Leak of test is a method which helps to determine the formation pressure limit where it actually breaks. Drillers run the drillpipe and circulate in open hole below the newly set casing and increase pressure to the point when formation breaks and mud starts to flow inside the formation. In Formation Integrity test (FIT)pressure increases to certain know level without actually breaking the formation. For the safety reason drillers usually do not perform the Leak off test but run FIT and use the pressure data to optimize mud weight for drilling the new section.

Hope this answer helps.
Please do not forget to RATE this answer.

REgards

Geology

All Answers


Answers by Expert:


Ask Experts

Volunteer


Syed Tariq Hasany

Expertise

MY HUMBLE REQUEST. BEFORE SENDING A QUESTION PLEASE READ THE FOLLOWING CAREFULY. ANSWERING ONLY PUBLIC QUESTIONS. Ask questions of exploration of Petroleum, and specific regions for specific answers about Pakistan, Central Asia, Middle East and Far East. Ask questions of Business side of the petroleum Geology. Love to guide students and also Career related issues PRIVATE QUESTIONS on thasany@yahoo.com I am not expert of Hard rocks (Igneous and metamorphic rocks)Volcanic activity and related petrology, mineralogy and its exploration. BE SPECIFOC WHAT YOU WANT TO KNOW AND ASK WITH DIGNITY AND RESPECT. Show me your determination and commitment to learn. PLEASE TRY TO WRITE RIGHT, PROPER AND CORRECT LANGUAGE. DO NOT USE TEXT(SMS)STYLE. Thanks TARIQ

Experience

Petroleum Exploration

Organizations
Petronas Carigali Sdn Bhd

Publications
In Pakistani and Asian Petroleum Confertence special Publications

Education/Credentials
BSc Honours in Geology and Master of Science degree in Petroleum Geology

Awards and Honors
Active member AAPG, SPE and PAPG Treasurer PAPG and AAPG Visiting Geoscientist

©2016 About.com. All rights reserved.