Engineering Design Project
1.1 Casing Introduction
In hydrocarbon recovery a fundamental aspect of the drilling
process is the selection of casing and casing depth both of which are a primary
engineering and economic concern for any exploration company.
Casing is a major structural component of any drilling well
and its importance to allow the following is outlined below:
Maintaining both the stability and integrity of the
drilling bore hole.
Preventing contamination by keeping both bore hole and
formation fluids in the correct places.
Controlling well pressures.
In drilling there are 6 main types of casing which are used which
are outlined below but are explained in greater detail throughout this section.
1. Conductor Casing.
Liner tieback casing.
Casing Depth Selection
Commencing well interpretation
the first part of the well design is choosing the casing depth selection for
each of the casings. To help determine the casing depth a graph of pressure
gradient v fracture porosity is conducted.
1.13 Conductor Casing Depth Selection
The conductor casing is the first casing inserted into the
well, it has the largest diameter of the casing and is the shortest. The
function of the conductor casing is to provide essential support for the tubes
run down the well bore whilst providing minimal bore hole support. The conductor
casing can be inserted in two ways by drilling a hole and cementing it in place
or subsequently driving it into the ground using a diesel-powered hammer.
Typical depth for conductor casing falls within the range of 100-300ft
however it has to be noted setting the depth of conductor casing is not always straightforward
and can often be very problematic, exploration companies often use alternative
solutions such as using two conductor strings. In addition, the depth of the
conductor string is often chosen using standard practice in the surrounding
area which has resultingly proven successful.