PETROLEUM FORMATION EVALUATION OVERVIEW
INTRODUCTION
As
we finding Hydrocarbon as discovery requires a lot of technical know-how,
precision tools, and a lot of money. it is dirty it is dangerous but we still
do it, although there's no guarantee will find hydrocarbons, but then again we
might call drilling oil that technically challenging just creates a hole in the
crust. In this book we need to evaluate that hole to determine and if that well
will be a commercial oil or gas well or just another dry hole.
FORMATION EVALUATION
PROCEDURE
Measure, Sample, and Test
We
will describe how we measure, sample, and test the actual rock formations and
their properties at the various depths of the hole as we drill downward. We
will show how we are able to use these measurements samples and test
evaluations at different stages and depths of the drilling program to help us
identify any reservoir rock that is present.
Measure, sample, and test the actual rock formations and
properties
Determine Rocks
and Fluid Properties
Once
it's identified will add this information to the mud log as we drill and then
compiled another more detailed electronic log after TD (Total Depth) has been
achieved, along the way we will continue collecting samples and performing
tests that help us determine the porosity, the permeability, and saturation of
types of fluid present in the rock.
Determine Rocks and Fluid Properties
The porosity, the permeability, and saturation of types
of fluid
Next
we will determine the depths, size, thickness, temperature, and pressure of
rock formation. finally by using the data from all of these procedures that
help us to evaluate the formation rock and from the results of the seismic
tests conducted earlier that gave us this area, we'll be able to calculate if
there are enough commercial quantities of hydrocarbon present to continue the
development of the well, as you might guess each of these measurements
samplings and tests required time and money.
The depths, size, thickness, temperature, and pressure
The seismic tests conducted earlier
MWD (Measuring
While Drilling) & LWD (Logging While
Drilling)
Because
it is usually the team of engineers who decide what procedures to run it is
they who must justify and not only the costs of these procedures but also the
down time in the drilling program. although the industry as fast and proving
the technology to run procedure during drilling in what is called measuring
while drilling (MWD), and logging while drilling (LWD) and many times it is still
necessary to round trip in and out of the hole with specialized equipment,
remember round tripping is when the drill string with the drilling bit and all
of the stands of pipe are pulled out of the wellbore for testing and then put
back in when it was finished.
Measuring while drilling (MWD), and logging while
drilling (LWD)
round tripping logging
The
information we learned from the different procedures will help guide us in
deciding whether or not to abandon or complete this well, regardless of whether
we find the next big reservoir or faced with a dry holes or data acquired and a
lot of time in expense will not go to waste. it will be uploaded into powerful
computers that can then be used to more accurately help predict where to drill
the next wildcat or development well.
Deciding to abandon or complete this well
DST (Drills Stem Test) & WFT (Wireline Formation
Tests)
Let’s
look at some of the traditional ways we acquire data, collect sample, and
performed tests so that we can evaluate what's in the formation. first during
drilling in what is known as open hole well or wells that have not then
prepared for production, data from the mud log is compiled by the driller, the
mud logger, and the site geologist. If zones of interest are detected, then
samples from cores are collected. Next while we are still in the open hole
phase after TD has been reached, open hole well logs, DST (drills stem test),
and WFT (wireline formation tests) are perform and interpreted.
The mud log is compiled by the driller, the mud logger,
and the site geologist
Open hole well logs, DST (drills stem test), and WFT
(wireline formation tests)
IP (initial potential) test
Finally
the last test, the IP (initial potential) test is conducted after the well has
been completed and equipped and what is known as cased hole or closed hole, but
before the well has been prepared for production. This very important test
allows the reservoir fluid volumes or flows and pressure measurements to be
accurately determined.
IP test run in Closed hole, before production
Petroleum Wells
let
we point out here that because very little data is available in wild cat wells,
the testing emphasis for them is someway different than for development wells.
for example in wildcat well more core samples are collected to help identify
rock formation, while in development wells more DST (drill stem tests) help
identify the various target zones and their characteristics.
Wildcat well more core samples are collected
Development wells more DST (drill stem tests)
Wild Cat Wells
When
gathering data from wild cat wells there for the most critical step is to
pinpoint potentially productive zones as they are penetrated. this can be a
very trying task drilling through an oil or gas some can easily go unnoticed
because the weight of the mud column can prevent reservoir fluids from entering
the wellbore thus obscuring the data. the company representative, the site
geologists and the mud engineer must be very vigilante closely to scrutinized
the rock cuttings or a rock pieces that have been crushed out of the formation
by the drill bit, and sent to the surface with the returning mud through the
annulus and make sure that this data is accurately recorded in the drilling
operation log.
Rock cuttings
Development Wells
A
particular challenge when drilling development wells is correlating new data
from a particular well with existing data from previously drilled nearby well.
because rock structures and formations can change dramatically from one location
to another it is not uncommon to encountered conflicting, confusing data, an
example of this might be when the porosity of the rock for a particular zone
changes from one well to another. When the geologist spots these variances or
differences, he'll be called on to explain this heterogenetic in the subsequent
constructed models.
Particular zone changes from one well to another
FORMATION
DRILLING DATA
There
are some methods used to collect data to evaluate wild cat well and development
wells in each method we’ll discuss how the need for different data will
influence how the data is hand and analyzed.
In
this book we'll limit our discussion to open hole wells. From the day we spud
in, we begin collecting drilling data, the record that we make is called the
drilling operations log or mud log, and this is continuous foot by foot or
meter by meter record of the hole as it is being drilled is refer to a mud
love. all important data gain from the cuttings and from the mud returns as
well as from the drilling operations or plotted against the depth on the same
strip chart of log so that they can be compiled on a chart, this drilling
operations log is a record with three main inputs from the driller, the mud
loger, and the site geologists.
Open hole and cased hole well
Drilling operations log
The Drilling Rate
Let
we discuss each input in a little more detail. we'll start with the input from
the driller, while rotating to kelly the driller measures how fast or how slow
the kelly goes down, for instance when drilling through hard rock the kelly
descends more slowly than when drilling through softer rock, the speed of the
kellys dissent is known as the drilling rate.
The speed of the kellys dissent is known as the drilling
rate
The
drilling rate is recorded on the log as the number of minutes per foot or meter
penetrated. Rate of penetration knowing this speed helps identify the type are
rock that is being penetrated and gives a general indication of the porosity of
that zone, hard rock for example is usually associated with shale or other cap
rock while softer rock is associated with sandstone or limestone which can be
oil or gas rich reservoir rock.
Rate of penetration identify the rock type and
indication of porosity
Hard rock, cap rock, and softer rock
Bottoms Up Circulation
When
the drill bit excess the non-porous hard rock and enters softer porous rock the
recording instruments in the log show this gap as you can see on the
illustration. This gap is called the drilling break, when this happens the
driller raises the drill bit a few feet breaking off from the bottom while
continuing to rotate and circulate mud, this circulating mud scoops up the last
of the cuttings and sends them to the surface this is called bottoms up
circulation. These cuttings from the last time of drill bit are then analyzed
by the site geologists, and our instrumental in helping it to determine future
steps in the drilling program. For example the geologists may make a
determination to core the next section of rock to be drill based on his
analysis of these cutting.
Bottoms up circulation
For
further read, you may get the book from amazon.
PETROLEUM FORMATION EVALUATION OVERVIEW
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