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Senin, 21 Januari 2019

PETROLEUM FORMATION EVALUATION OVERVIEW


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

https://www.amazon.com/PETROLEUM-FORMATION-EVALUATION-OVERVIEW-1/dp/1792196466

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