Category Archives: Oil & Gas

The Mississippian Period and Its Rocks

The term Mississippian is US term used to describe the early Carboniferous period. The term Carboniferous is used in England to identify the period spanning 359.2 to 299 million years ago when the earth was rich with deposits of coal. These deposits were found at that time all over Northern Europe, Asia, and Midwestern and Eastern North America.

The Mississippian Subsystem is differentiated from the Pennsylvanian by the appearance of the conodont Declinognathodus noduliferus, the ammonoid genus Homoceras, and the foraminifers Millerella pressa and Millerella marblensis, though these markers apply only to marine deposits. The distinction between the Mississippian and Pennsylvanian subsystems may also be illustrated by a break in the flora due to transitional changes from a marine to a more terrestrial environment.

The stratigraphy of the Mississippian is distinguished by shallow-water limestones. Some of these limestones are composed of parts of organisms, primarily the remains of crinoids that thrived in the shallow seas. Other limestones include lime mudstones, composed of the carbonate mud produced by green algae, and oolithic limestones, composed of calcium carbonate in concentric spheres produced by high wave energy. Also found in Mississippian strata, though not as common, are sandstones (sedimentary rock composed of quartz sand and cemented by silica or calcium carbonate) and siltstones (rock composed of hardened silt).

At left, scientists in a coal mine have color coded the successive layers of coal ball formation. Each layer represents an individual flood event in the coal swamp. On the right, a scientist observes the evidence of glacial and interglacial strata in Kansas. Glacial periods result in lowered ocean levels, while interglacial periods result in a rise in ocean levels, covering the continental shelf with shallow seas.
Coal beds, which can be up to 11 to 12 meters thick, characterize the late Carboniferous. The forests of seedless vascular plants that existed in the tropical swamp forests of Europe and North America provided the organic material that became coal. Dead plants did not completely decay and were turned to peat in these swamp forests. When the sea covered the swamps, marine sediments covered the peat. Eventually, heat and pressure transformed these organic remains into coal. Coal balls, pockets of plant debris that were preserved as fossils and not converted to coal, are sometimes found within the coal layers.

Multiple transgressions and regressions of the Pennsylvanian seas across the continent can be seen in the rocks, and even counted, because they leave a telltale sequence of layers. As sea levels rise, the layers may go from sandstone (beach), to silty shale or siltstone (tidal), to freshwater limestone (lagoon), to underclay (terrestrial), to coal (terrestrial swampy forest). Then as sea levels fall, one may see a shale (nearshore tidal) grade to limestone (shallow marine) and finally to black shale (deep marine).

Index fossils are the remains of plants and animals that characterize a well-defined time span and occur over a wide range of geography. Fossils of marine life characterize the Mississippian, as shallow epicontinental seas covered the United States at that time. These fossils include solitary corals and Syringopora, tubular colonial corals. Other fossil colonial corals include Stelechophyllum and Siphonodendron. Because conodont fossils are distributed all over the world, they are utilized internationally to date Mississippian rocks.

According to the University of California Museum of Paleontology, “The Mississippian environment of North America was heavily marine, with seas covering parts of the continent. As a result, most Mississippian rocks are limestone, which are composed of the remains of crinoids, lime-encrusted green algae, or calcium carbonate shaped by waves.”

“The stratigraphy of the Mississippian is distinguished by shallow-water limestones. Some of these limestones are composed of parts of organisms, primarily the remains of crinoids that thrived in the shallow seas. Other limestones include lime mudstones, composed of the carbonate mud produced by green algae, and oolithic limestones, composed of calcium carbonate in concentric spheres produced by high wave energy. Also found in Mississippian strata, though not as common, are sandstones (sedimentary rock composed of quartz sand and cemented by silica or calcium carbonate) and siltstones (rock composed of hardened silt).”

Texas’ Oil Production

Texas has produced great quantities of oil in the past decade with an average of some 500,000,000 barrels of oil yearly according to the Energy Information Administration of the US Department of Energy. This was a product of the crude oil production reported by the operators to the Railroad Commission of Texas annually every 15th of February.

In the last 6 years, 2014 has brought in the highest crude oil production on a month-on-month basis. For the month of January, it produced 69,903,539. For the month of February, it produced some 64,058,704 barrels. For March, it produced 71,589,704 barrels. For April, it produced, 70,506,631 barrels. For May, it produced 72,299,887 barrels. In June, it produced 70,108,403 barrels. At last measure in July, it was estimated that Texas produced 69,573,013 barrels of oil.

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In 2013, a total of 703,119 barrels were produced with a daily average of 1,926,000 barrels. It had some 179,797 wells producing these. Each of these well produced an average of 10.71 barrels a day. There was a 32.19% change in production in comparison to the 533,141,000 barrels of oil produced in 2012.

In recent history, the 2013 production of oil has been the highest recorded. The last highest yearly production was recorded in 1972 when 1,263,412 barrels of oil were produced. This was the highest production since well drilling began in Texas in 1935. of February.

Texas Field Production of Crude Oil (Thousand Barrels)
Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
  1981 80,609 72,591 80,734 77,344 79,890 77,030 78,640 78,356 76,017 78,364 75,135 77,640
  1982 77,306 70,503 78,298 75,983 77,507 74,349 76,378 76,110 74,624 76,561 74,496 76,102
  1983 75,776 69,034 76,046 73,833 75,263 73,020 74,932 74,393 72,726 74,850 72,827 70,211
  1984 76,531 70,374 75,510 72,756 74,806 72,228 74,382 74,123 71,958 74,016 72,024 74,466
  1985 73,331 66,371 74,105 73,839 74,004 70,958 73,337 73,533 70,643 73,585 71,690 73,822
  1986 74,135 66,752 73,344 69,397 70,407 66,802 68,621 67,529 64,891 66,638 64,604 66,475
  1987 66,135 60,010 66,167 63,738 64,459 61,837 63,677 63,399 61,622 64,129 62,107 63,682
  1988 63,922 59,979 63,853 61,281 62,750 60,347 61,624 61,476 59,019 61,450 59,159 60,635
  1989 60,740 53,515 59,812 57,725 59,073 56,383 58,015 57,916 55,717 57,467 55,925 55,881
  1990 58,072 52,687 57,594 55,382 57,044 54,665 56,603 57,292 55,515 58,804 56,998 57,822
  1991 59,433 54,071 59,299 57,138 58,502 55,333 57,078 57,332 55,302 57,160 55,424 56,544
  1992 56,323 52,552 56,220 54,054 54,953 52,661 54,505 54,719 52,929 54,834 52,601 54,274
  1993 54,148 48,839 53,801 51,690 52,838 50,734 51,722 51,853 50,005 51,726 50,183 51,551
  1994 51,754 46,561 51,465 49,384 50,644 48,323 49,488 49,347 47,681 48,888 47,771 49,430
  1995 49,056 44,190 48,410 46,696 47,706 45,594 46,681 46,620 45,107 47,110 45,725 46,751
  1996 46,721 43,547 47,159 45,382 46,406 44,396 45,439 45,202 44,037 45,663 43,803 45,587
  1997 45,150 41,756 45,840 44,467 45,629 44,141 45,305 45,012 43,976 45,536 44,460 45,313
  1998 45,909 41,312 45,140 43,016 43,723 41,599 41,721 41,772 40,185 41,157 39,708 39,420
  1999 39,197 35,443 38,576 37,050 38,147 36,136 37,374 37,109 36,442 38,109 37,180 38,470
  2000 38,241 36,030 38,258 36,836 37,606 36,234 37,121 37,177 35,866 36,999 35,848 37,181
  2001 37,020 33,270 36,603 35,464 36,204 34,606 35,747 35,622 34,127 35,770 34,253 35,611
  2002 35,477 31,959 34,903 33,653 34,596 32,975 33,876 33,968 32,904 33,980 33,233 34,252
  2003 34,336 31,046 34,578 33,273 34,030 32,560 33,571 33,529 32,843 34,071 32,850 33,977
  2004 33,797 31,700 33,758 32,461 33,223 31,709 32,762 32,838 32,023 33,090 32,073 33,281
  2005 33,740 30,718 34,033 32,706 33,439 32,094 32,887 33,012 31,152 33,176 32,387 33,257
  2006 33,639 30,439 33,691 32,383 33,158 31,960 32,932 32,806 32,121 33,438 32,506 33,408
  2007 32,790 30,191 33,501 32,481 33,244 31,743 32,825 32,977 32,075 33,229 32,515 33,701
  2008 33,914 32,020 34,549 33,397 34,404 32,920 34,429 34,421 31,673 34,889 34,243 35,149
  2009 35,121 31,590 34,665 33,306 33,765 32,131 32,952 33,069 32,432 33,499 33,022 33,792
  2010 34,053 31,389 35,237 34,114 35,528 34,155 35,728 36,162 35,732 37,714 37,291 39,646
  2011 39,726 34,341 41,403 40,396 43,162 42,011 44,503 46,098 46,002 49,360 49,603 52,202
  2012 53,199 51,142 55,511 55,997 59,230 58,411 61,964 63,623 62,676 66,734 66,448 69,252
  2013 70,421 65,437 73,880 72,359 76,968 75,493 79,783 80,685 79,447 82,389 80,135 86,599
  2014 88,047 80,835 90,944 89,412 93,841 92,215 96,168



= No Data Reported;  = Not Applicable;  NA = Not Available;  W = Withheld to avoid disclosure of individual company data.

American Energy Production Shows No Signs Of Slowing Down

“Oil output will respond very slowly to a drop in oil prices,” Bjornar Tonhaugen, vice president for oil and gas markets at Rystad Energy, wrote in a report released this week. “Markets may even be oversupplied next year more than previously thought.”

The decrease in oil and gas prices may have sent oil company stocks tumbling, however oil experts have claimed that the American energy production is not slowing down.

Even after a drop of as much as 25 percent in oil prices since early summer, several government and private reports say that it would take a drop of $10 to $20 a barrel more — to as low as $60 a barrel — to slow production even modestly.

On the downside, taxes and royalties on oil will decline, potentially cutting into the finances of oil-producing states like Texas, Alaska, Oklahoma and North Dakota. And it will continue to put pressure on the Organization of the Petroleum Exporting Countries to cut output to support prices, as well as cause economic pain to big producers like Russia, Venezuela and Iran.

Slowing American oil production is like slowing a freight train moving at high speed. The current production of 8.7 million barrels a day, the highest in nearly a quarter-century, is more than a million barrels a day higher than it was only a year ago. Most companies make their investment decisions well in advance and need months to slow exploration because of contracts with service companies. And if they do decide to cut back some drilling, they will pick the least prospective fields first as they continue developing the richest prospects.


The Energy Department this week reported that only 4 percent of shale production in North Dakota, Texas and other states needed an oil price above $80 a barrel for producers to break even on investments. One reason is that improved efficiencies in hydraulic fracturing and other modern production techniques have increased the output of each new well month after month in recent years.


Problems and Solutions: Oil Swabbing

swab017.jpg.Swabbing is the act of pulling fluid from the well bore through the use of wire rope and cup assembly. Swabbing equipment includes a swabbing assembly, lubricator with an oil saver, and shut-off valve on the well, also called a swabbing valve.

General precautions during all swabbing operations:

  • Conduct swabbing operations during daylight hours.
  • Keep all personnel clear of the derrick or within six feet (two meters) of the wellhead during swabbing operations.
  • Locate swab tanks at least 100 feet (30 meters) from the well, where location allows.

Potential Hazard:

  • Loss of well control.

Possible Solutions:

  • Use appropriate equipment, rated for the expected pressures, to shut in the well.
  • Inspect lubricators, swages, and unions for defects such as cuts, corrosion, and thread damage before use.
  • Adjust oil savers by remote control with a hydraulic pump placed safely away from the wellhead.
  • Train all personnel in emergency evacuation procedures.

Potential Hazard:

  • Fire, explosive, or respiratory hazard from leakage or venting of oil or gas from tanks, lines or lubricator.

Possible Solutions:

  • Place fire extinguishers in accessible positions.
  • Move sources of potential ignition (such as, open fires for melting of babbitt) to designated areas at a safe distance from the wellhead or flammable liquid storage areas such as the swab tank before swabbing.
  • Make provisions to contain spilled flammable liquids.
  • Monitor the oil saver for wear and potential leakage.
  • Remove all spillage of flammable liquids from equipment, cellars, rig floor, and ground area adjacent to the wellhead.
  • Wear proper PPE, including respiratory protection, as required.

Potential Hazard:

  • Being struck by a pressurized line.
  • Being exposed to a high-pressure connection failure caused by mismatched or excessively worn hammer unions.

Possible Solutions:

  • Avoid approaching, walking over or standing near pressurized lines.
  • Securely anchor pressurized lines to prevent whipping or bouncing caused by pressure surges.
  • Use proper equipment inspection techniques to include hammer unions (Note: This is a particular problem with 602 and 1502 and others, as they will couple but will not hold beyond the lower pressure rating number).
    • High Pressure Lines and Hammer Unions. International Association of Drilling Contractors (IADC) Alert 98-01, (1998).
    • More On Mismatched Hammer Unions. International Association of Drilling Contractors (IADC) Alert 99-33, (1999).
    • Additional Serious Incidents With Mismatched Hammer Unions. International Association of Drilling Contractors (IADC) Alert 00-15, (2000).

Potential Hazard:

  • Being struck by pressurized fluids or the lubricator when removing the lubricator from the well.
  • Getting strains and sprains from handling the lubricator.

Possible Solutions:

  • Close the shut-off valve and bleed the pressure from the lubricator before removing it.
  • Use a lubricator that will allow removal of the swab or other tools with the well shut in (valve closed).
  • Use a dolly or other method to minimize manual handling of the equipment.

Potential Hazard:

  • Pinching fingers between swab assembly and lubricator when changing swab cups or mandrels.

Possible Solutions:

  • Use a winch line, where available, not the swab line, to handle the lubricator.
  • Use a lubricator that will allow removal of the swab or other tools with the well shut in (valve closed).

Additional Information:

  • Standards. American Petroleum Institute (API).
    • RP 54, Occupational Safety for Oil and Gas Well Drilling and Servicing Operations. (2007, March).


Swabbing a Well: What Is It and Why Do We Do It?

In oil drilling, pressurized liquid is used to cool the drilling equipment, move soil and debris out of the oil’s path, and ultimately, force the oil into a path of the liquid’s creation. In order to get the process of oil production officially started or restarted, one must engage in oil well control. One way to do this is to initiate a process called well swabbing.  This is done so that the liquids that have pooled in the well during the pressurized liquid “drilling” and “cleaning” will be removed from the oil well and force the oil to gush out due to the pressure build up in the well shaft.



Gas and oil well pumping or swabbing devices to remove oil from an oil and gas well relying on the residual gas pressure in the well to lift the swabbing device and the attendant column of oil thereabove in said oil well casing are exemplified byU.S. Pat. Nos. 4,813,485, Coyle, 4,528,896, Edwards, 4,070,134, Gramling, and 3,179,022, Bloudoff, as well as others. Many of these devices contain a valve which, when open, permits the inherent weight of the swabbing device to cause it to sink downwithin the oil well casing through the accumulated oil and gas therein to a predetermined position near the bottom of the casing, at which time a stop or a pressure sensor will cause the valve to be closed, and as gas pressure builds up underneath theswabbing device, it and the column of oil thereabove will be raised to the surface, at which time the valve will again be opened, either automatically or manually, and the swabbing device will repeat the cycle.There are a number of stops for actuating the valve in the swabbing device disclosed in the prior art, some of which are retrievable. However, many are not. (ref:

When a well is swabbed a swabbing rig is backed as closely as possible into the production zone. According to Tiger General, these swabbing rigs normally have a winch with a cable and a foldable mast with a pulley on top. The operator raises the mast and moves it until it is aligned with the center of the well. Next, the operator lowers the cable in and out of the well via the ‘winch drum’.“ This process forces the oil to gush out from the bottom hole as the pressure is increased due to the vacuum created by the process. A batch of pumped out liquid is called a run. An average oil well usually has 6 runs before the oil or gas can properly gush out of the bottom hole.