Michael Hudson - Reservoir Engineer
In choosing a company to perform a drill stem test it is important to choose a reputable company with experienced testing personal and an experienced reservoir analyst.
The reservoir analyst should be experienced not only in reservoir evaluation but should be an experienced tester so he can identify with the mechanics and special conditions in the running of a drill stem test.
In 1980 Michael Hudson started a company called Data Reporting Services or DRS. Prior to that he spent 12 years as a down hole tool technician, a drill stem tester and for 5 years was the Director of Technical Services of an international drill stem testing company. During that time Michael and his staff processed over 20,000 drill stem tests.
Since starting DRS in 1980 Michael Hudson has processed over 50,000 drill stem tests nationwide and is the industry leader in drill stem test analysis and problem solving.
In the early 1980’s he saw the need for a more accurate method for determining a production rate from a DST. Up until that time most technicians simply calculated a rate based upon the liquid recovery in the drill string after the test which generally gave a daily rate which was anywhere from 25% to 40% too high. After studying hundreds of DST’s and subsequent production data he formulated a method for calculating a rate which was far more accurate and as a consequence produced more accurate calculations for other reservoir properties such as Permeability and Skin.
In 1991 he was one of the inventors of a software program called “”. This program will digitize analog charts from a mechanical pressure gauge with an accuracy of 0.0008”. Far more accurate than any other method of digitizing charts. Depending on clock speed this program will provide thousands of data points for a far more accurate reservoir analysis.
The first step in computer aided drill stem test evaluation is of course, data preparation. The numeric data is imported into the evaluation program and is viewed and analyzed for accuracy. Any anomalies should be noted and evaluated. It is important that the reservoir analyst be experienced in the mechanics and the running of drill stem test tools to determine if the test is mechanically sound. Any mechanical anomalies such as tool plugging, slippage, packer seat leaking, etc. needs to be identified by the analyst as these problems will effect the accuracy of the evaluation and may even make accurate evaluations impossible.
After the data has been prepared and any anomalies identified the evaluation process can begin. A drill stem test is unique and special care must be taken for a proper reservoir analysis. For example, determining an accurate liquid rate can be difficult. There are several methods for determining this rate depending on the individual test. Probably the least accurate of which is simply taking the amount of fluid that has entered the drill stem during the test and calculating a daily rate, since rat hole fluid and sediments probably entered the string when the tool was initially opened. Also, most times, porosity and pay thickness are not known at the time of the test and will need to be estimated.
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BJ's Drill Stem Testing