Drill stem tests

The drill pipe itself can be used for formation evaluation (Drill Stem Testing— DST), well stimulation (fracturing, acidizing), and fishing operations. 

BHA — Change bottom hole assembly DMF — Down hole motor failure DSF — Drill string failure DST — Drill stem test DTF — Down hole tool failure LOG — Run logs CM — Condition mud CP — Core point DP — Drill plug FM — Formation change... 

Generally, a drill stem test is carried out—either in the Open hole or after the hole has been cased. However, the case bole test is the most reliable. 

Basically, the drill stem test involves attaching a tubing assembly to the end of the drill pipe, isolating the lest zone with rubber packers, and perforating the zone. The tool is then opened so that the fluids or gas in die formation can How up the drill pipe for metering at the surface. During this process, extensive pressure measurements are taken, which can help to indicate the extent of the reservoir and the rate at which the hydrocarbons could be recovered. Prior to describing how a well is finally completed (if the hole is not dry ), it is in order to describe the forces utilized to transfer the oil from the reservoir to the surface. 

Baskin D. K. and Jones R. W. (1993) Prediction of oil gravity prior to drill stem testing in Monterey Formation reservoirs. Offshore California. Am. Assoc. Petrol. Geol. Bull. 77, 1479-1487. 

Direct pressure measuring devices Pressure bombs Drill-stem test Wire-line formation test When well is tested or completed... 

Pore pressure measurements have been compiled from drill stem tests (DST) and repeated formation tests (RFT) for the presumed reservoir zones in the study area. Since DST and RFT, are mn only in the reservoir zones, we have gathered information about fluid pore pressure through mud weight densities. The fluid pressures of investigated wells are summarized in Fig. 5. 

The existence of fresh water beneath the Atlantic Ocean, to the edge of the U.S.A. continental shelf, has been well documented in the JOIDES and AMCOR drill holes (Manheim, 1967 Hathaway et al., 1979 Kohout, 1981 Pauli and Dillon, 1981). New electrical-logging data from the COST GE-J well confirm the existence of brackish water in the upper 900 m. Moreover, a special agreement by Tenneco Oil Co. permitted the U.S. Geological Survey to run a drill-stem test at 350-m depth, in a wildcat well (Fig. 1, T) 85km seaward of Jacksonville, Florida. A drill-stem test confirmed presence of brackish water having less than half the salinity of seawater (R. Johnston, pers. commun., 1979). 

The study area comprises 28,000km in southeastern Alberta (Fig. 1). Rocks of interest to this study range in age from Tertiary to Carboniferous. The stratigraphic sequence, however, does contain older Paleozoic and Precambrian rocks at depth. With the exception of certain carbonate rocks in the Upper Paleozoic, the dominant lithology is shale with occasional sandstone units and minor coal. Some of the sandstone units contain substantial quantities of oil and gas. As a result of continued exploration for and development of these resources, a tremendous quantity of conventional lithologic log, geophysiced log, core and drill-stem test data is available for this area. 

Some preliminary work has been completed to explain the origin of the permeability of the sandstone units. In the Bow Island Formation, an attempt was made to correlate conductivity values from drill-stem tests with the estimated true formation resistivity determined from electric logs. The lack of correlation, however, suggests that fracture permeability may be prevalent. 

Evaluation of the vertical flow components is difficult because the head calculations from drill-stem test data probably have errors associated with them of the same order of magnitude as the actual differences in head. It is probably possible, however, to make certain generalizations. The flowing-wells completed in the MUk River aquifer provide good evidence of an upward flow component from the aquifer toward the ground surface. It is also possible that water is also leaving the aquifer from the bottom and moving downward. The Bow Island Formation appears to be a potential low with flow directed upward towards it from the Mannville and downward from the Second White Specks, Medicine Hat Sandstone and Milk River Formation. 

In this description of the geochemistry of formation water, we will consider first the distribution of Na, Cl and SOV ions which are some of the most dominant major-ion species and second the stable-isotope ratios of D/H and O/ O. The basic data for the ion chemistry come from a set of 240 good-quality unpublished analyses of samples collected mainly from drill-stem tests but some from separators. These data are supplemented by 1500 analyses of formation water gathered over the last 20 years by the... 

The preliminary assay provides general data on the oil and is based on simple tests such as distillation range, water content, specific gravity, and sulfur content that enable desirable or undesirable features to be noted. This form of assay requires only a small quantity of sample and is therefore particularly useful for the characterization of oil field samples produced from cores, drill stem tests, or seepages. 

The data presented come from analysis of 351 petroleum fltxids from drill stem test (DST), repeat formation test (RFT) and production tests from basins in the North Sea, China, West Africa, USA and Germany. All data are quantitative measurements of the concentrations of various saturated and aromatic hydrocarbons in dead (separator degassed) oils and condensates from these petroleum systems. Concentrations are reported relative to the dead fluid, as would normally be the case. 

Formation pressure data were obtained from repeat formation tester (RFT) or modular dynamic tester (MDT) measurements of numerous deep wells in the Central North Sea. These data were used as the primary pressure dataset as they are the most accurate pressure measurements possible down-hole. The MDT/RFT wireline tool takes a pressure reading within a permeable formation, by setting a seal at a precise depth determined by using an accompanying gamma ray tool for depth correlation. Drill stem test (DST), mudweight data and kick (influxes of pore fluids into the wellbore) information was also used where RFT or MDT data were not available or of very poor quality. A summary of the various approaches used to derive formation pressures is provided by Holm (1998). 

Potential productive zone are isolated and performed formation testing and drill stem testing. 

A common problem with many oil exploration wells is that they are drilled with oil-based drilling muds, or are contaminated with other anthropogenic substances. These can make evaluation of oils recovered from drill stem tests or by solvent extraction of reservoir lithologies very difficult, due to overprinting of the crude oil. Analysis of oil inclusions can avoid these problems because the fluid inclusions are trapped before drilling, so extraneous or drilling contaminants can be removed... 

Badry et al. 1993), but no tools are currently equipped with electrodes for in situ measurements of pH. pH electrodes that operate at high temperatures (e.g., 200-300 C) are currently being developed (Bourcier et al. 1987), and research into their use during subsurface drill-stem tests of formation waters may provide the best results in determining this important variable. 

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