Question

Why is bottom hole treating pressure important to monitor?

Answer
By Krystal Nanan | Last updated: September 11, 2019

The first step in setting up a hydraulic fracture job is knowing the expected treatment rates and pressures. One of the most influential factors in determining these parameters is the bottom-hole treating pressure (BHTP). (Read Bottom Hole Treatment Pressure: What It Means to Your Fracking Project.)

During the early stages of hydraulic fracturing, small explosive charges from a perforating gun are set off in the horizontal bore, creating small, shallow holes in the underground shale formation. (Read The Hydraulic Fracturing Technique: Things You Should Know.)

High-pressure fluid is then pumped into the perforations, causing the shale layers to crack horizontally and vertically. In addition to expanding fractures into the shale, the fluid pressure must be able to keep the fractures open to allow oil and natural gas to flow into the wellbore for extraction. (Read The Essentials to Drilling and Boring Wells.)

The BHTP is defined as the amount of pressure required to fracture the rock during hydraulic fracture operations. It is essentially the pressure along the face of the fracture responsible for keeping the fracture open. At a minimum, the BHTP must be more than the fracture’s closing pressure, which is the minimum pressure needed for the fracture to remain open.

The BHTP needs to be continuously monitored as it is a crucial parameter used to determine the surface-treating pressure (STP). Correct estimation and maintenance of the BHTP is, therefore, a significant factor in the success of a hydraulic fracking project.

By knowing the STP, engineers can determine the real-time pressure required by the surface pressure transducer on the mainline. (Read Carrying Out In-Situ Stress Measurements: Hydraulic Fracturing Vs. Overcoring Methods.)

Additionally, once the STP is estimated, operators can ensure that the amount of hydraulic horsepower (HHP) available on-site during the hydraulic fracture job is adequate.

BHTP can be calculated by:

BHTP = FG x TVD

Where:

FG = Fracture gradient (the pressure gradient at which the formation breaks).

TVD = True vertical depth.

With the BHTP known, the STP can then be determined using the following formula:

STP = BHTP + Pf + Pnet – Ph

Where:

Pf = Total friction pressure.

Pnet = Net pressure (excess pressure required to extend the fractures).

Ph = Hydrostatic pressure.

Share this Q&A

  • Facebook
  • LinkedIn
  • Twitter

Tags

Horizontal Directional Drilling Trenchless Methods Boring Operations Maintenance Fracture Mechanics Drilling Fluid Geotechnical Site Investigation Expert Content

Written by Krystal Nanan | Civil Engineer

Profile Picture of Krystal Nanan

Krystal is a civil engineer and project manager with an MSc in Construction Engineering and Management. Her experience includes the project management of major infrastructure projects, construction supervision, and the design of various infrastructure elements including roadway, pavement, traffic safety elements and drainage.

More Q&As from our experts

Related Terms

Related Articles

Term of the Day

Core Puller

Core puller is an equipment that is used to pull the core sample obtained during geotechnical investigation for the purpose...
Read Full Term

Don’t Miss the Latest From Trenchlesspedia!

Subscribe to our newsletter to get expert advice and top insights into every aspect of trenchless construction and rehabilitation. We create top educational content for and about the trenchless industry, insuring you have the knowledge you need for successful trenchless projects.

Resources
Go back to top