Wells – Processes – Sampling well fluid
Reexamination Certificate
2001-03-15
2003-05-06
Bagnell, David (Department: 3672)
Wells
Processes
Sampling well fluid
C166S065100, C166S165000, C175S059000
Reexamination Certificate
active
06557632
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the art of earth boring and the collection of formation fluid samples from a wellbore. More particularly, the invention relates to methods and apparatus for collecting a deep well formation sample and preserving the in situ constituency of the sample upon surface retrieval. Once the sample is retrieved, this invention describes methods and apparatus for isolating and extracting a sub-sample for a field determination of the quality of the primary sample without altering the primary sample composition.
2. Description of Related Art
Earth formation fluids in a hydrocarbon producing well typically comprise a mixture of oil, gas, and water. The pressure, temperature and volume of formation fluids control the phase relation of these constituents. In a subsurface formation, high well fluid pressures often contain gas within the oil above the bubble point pressure. When the pressure is reduced, as by raising an in situ captured sample of the formation fluid to the surface, the dissolved gaseous compounds separate from the liquid phase sample. The accurate measure of pressure, temperature, and formation fluid composition from a particular well affects the commercial interest in producing fluids available from the well. The data also provides information regarding procedures for maximizing the completion and production of the respective hydrocarbon reservoir.
Certain techniques analyze the well fluids downhole in the wellbore. U.S. Pat. No. 5,361,839 to Griffith et al. (1993) disclosed a transducer for generating an output representative of fluid sample characteristics downhole in a wellbore. U.S. Pat. No. 5,329,811 to Schultz et al. (1994) disclosed an apparatus and method for assessing pressure and volume data for a downhole well fluid sample.
Other techniques capture a well fluid sample for retrieval to the surface. U.S. Pat. No. 4,583,595 to Czenichow et al. (1986) disclosed a piston actuated mechanism for capturing a well fluid sample. U.S. Pat. No. 4,721,157 to Berzin (1988) disclosed a shifting valve sleeve for capturing a well fluid sample in a chamber. U.S. Pat. No. 4,766,955 to Petermann (1988) disclosed a piston engaged with a control valve for capturing a well fluid sample, and U.S. Pat. No. 4,903,765 to Zunkel (1990) disclosed a time delayed well fluid sampler. U.S. Pat. No. 5,009,100 to Gruber et al. (1991) disclosed a wireline sampler for collecting a well fluid sample from a selected wellbore depth, U.S. Pat. No. 5,240,072 to Schultz et al. (1993) disclosed a multiple sample annulus pressure responsive sampler for permitting well fluid sample collection at different time and depth intervals, and U.S. Pat. No. 5,322,120 to Be et al. (1994) disclosed an electrically actuated hydraulic system for collecting well fluid samples deep in a wellbore.
Downhole temperatures in a deep wellbore often exceed 300 degrees F. When a hot formation fluid sample is retrieved to the surface at 70 degrees F., for example, the resulting drop in temperature causes the formation fluid sample to contract. If the volume of the sample is unchanged, such contraction substantially reduces the sample pressure. A pressure drop changes the in situ formation fluid parameters thereby inducing phase separation between liquids and dissolved gases within the formation fluid sample, for example. As another example, dramatic pressure changes in a formation sample may precipitate dissolved solids such as waxes and asphaltines. These types of phase separation represents significant and irreversible changes in the formation fluid characteristics, and reduces the ability to evaluate the actual properties of the formation fluid.
To overcome this limitation, various techniques have been developed to maintain pressure of the formation fluid sample. U.S. Pat. No. 5,337,822 to Massie et al. (1994) teaches the concept of pressurizing a formation fluid sample with a hydraulically driven piston powered by a high pressure gas. Similarly, U.S. Pat. No. 5,662,166 to Shammai (1997) teaches the use of a pressurized gas to charge the formation fluid sample. U.S. Pat. Nos. 5,303,775 (1994) and U.S. Pat. No. 5,377,755 (1995) to Michaels et al. disclose a bi-directional, positive displacement pump for increasing the formation fluid sample pressure above the bubble point so that subsequent cooling does not reduce the fluid pressure below the bubble point.
More recently, U.S. patent application Ser. No. 09/648,410 by Paul A. Reinhardt, filed Aug. 25, 2000, has disclosed a multiple tank sample extraction system in which each sample tank in a magazine carrier has a two stage piston chamber by which the in situ wellbore pressure of a deep well fluid within a sample retrieval chamber is amplified to overcome the contraction consequences of removing a sample of deepwell fluid to the earth surface. At the interface of the apparatus where each of several independently removable tanks is severed from a common charging magazine, a small quantity of high pressure formation fluid is isolated in a sample transfer conduit between a magazine distribution valve and a tank closure valve. Although both valves are closed when an individual tank is removed from its respective magazine alcove, this small quantity of fluid is vented to the atmosphere as a preparatory step to severance of the tank from the magazine for individual transport and sample testing.
Although the quantity of this atmospherically vented fluid is small, it is important to observe the nature and quality of the vented fluid as a qualitative clue to the fluid within the main body of the sample chamber. Notwithstanding extreme care in downhole sampling procedures, it is still possible for the wireline magazine to return with contaminated samples in one or more tanks. Such contamination may take the form, for example, of water seepage from other strata, mud cake deposited against the borehole wall or wellbore drilling fluid. Filtrate from oil based drilling mud is especially a problem.
Samples must be representative of fluid in the formation and consequently must be substantially free of contaminates from drilling operations. In particular, samples need to contain less than a few percent of filtrate from an oil base mud for that sample to be representative of the formation fluid. Usually, 10% contamination in a sample is too much for a reliable pressure/volume/temperature analysis. Acquisition of a formation fluid sample this pure and greater is difficult to obtain. Moreover, it is essential to know the relative contamination in a sample to a reasonable degree of certainty at the time the sample is extracted. The physical and intellectual effort committed to extracting a deepwell sample is of such magnitude that repetition of the effort is to be avoided if possible. Consequently, it is desirable to obtain a small sub-sample of the recovered fluids to determine whether or not the contamination level is sufficiently low to warrant laboratory analysis. It is imperative that this sub-sample be extracted without altering the physical properties of the primary sample reserved for a more expansive laboratory analysis.
It is an object of the present invention, therefore, to controllably secure a portion of the transfer conduit fluid for the purpose of field analysis. Also an object of the present invention is provision of means to evaluate the nature of a fluid sample confined within a high pressure tank chamber without risking the integrity of the sample composition.
SUMMARY OF THE INVENTION
These and other objects of the present invention as will become apparent from the following description of the preferred embodiments are accomplished by a deep well sampling system that is capable of isolating the last portion of sample fluid that is collected into a sample chamber. The sampling system extracts formation fluid directly from the desired formation through a probe that is pressed into the borehole sidewall. This formation fluid is pumped by a downhole equipment pump dedicated to the wellbore equipment al
Bagnell David
Baker Hughes Incorporated
Gay Jennifer H
Madan Mossman & Sriram P.C.
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