Spraberry Trend
Encyclopedia
The Spraberry Trend is a large oil field in the Permian Basin of west central Texas
, covering large parts of six counties, and having a total area of approximately 2500 square miles (6,475 km²). It is named for Abner Spraberry, the Dawson County farmer who owned the land containing the 1943 discovery well. The Spraberry Trend is itself part of a larger oil-producing region known as the Spraberry-Dean Play, within the Midland Basin. Discovery and development of the field began the postwar economic boom in the nearby city of Midland
in the early 1950s. The oil in the Spraberry, however, proved difficult to recover. After about three years of enthusiastic drilling, during which most of the initially promising wells showed precipitous and mysterious production declines, the area was dubbed "the world's largest unrecoverable oil reserve."
In 2007, the U.S. Department of Energy ranked The Spraberry Trend third in the United States by total proved reserves, and seventh in total production. Estimated reserves for the entire Spraberry-Dean unit exceed 10 Goilbbl, and by the end of 1994 the field had reported a total production of 924 Moilbbl.
and the Edwards Plateau
. As most often defined, the Spraberry includes portions of Irion, Reagan
, Upton
, Glasscock, Midland, and Martin Counties, although the underlying geologic unit also touches Dawson, Crockett, and Andrews Counties. Elevations are generally between 2,500 and 3000 feet (914.4 m) above sea level, and the terrain varies from flat to rolling, with occasional canyons, known locally as "draws", cutting through the plateau. Drainage is to the east, via the Concho River
to the Colorado River
. The climate is semi-arid
. Native vegetation includes scrub and grasslands, with trees such as cottonwoods along the watercourses.
Aside from activities associated with oil production, transport, and storage, predominant land use in the area includes ranching and farming.
and calcareous or silicate mudstone
and siltstone
, deposited in a deep water environment distinguished by channel systems and their associated submarine fans, all of Permian
age. The sands are interbedded with shale
s, and typically pinch-out updip. Unlike many of the oil-bearing rocks of West Texas, however, the Spraberry Sands have very low porosity
and permeability, both of which hamper oil recovery. The rocks are naturally fractured, further complicating hydrocarbon flow. Oil has accumulated in stratigraphic traps, migrating upward from source rocks until encountering impermeable barriers, either in the internal shaly members or the overlying impermeable formation.
Shaly rocks make up a total of 87% of the Spraberry, with the oil-bearing sands and siltstones present sometimes in thin layers between them. The best-producing zone is at an average depth of 6800 feet (2,072.6 m) across the entire region, which is about 150 miles (241.4 km) long by 70 wide.
Unfortunately for most of the speculators, investors, and outside independent oil companies, most of the newly drilled wells behaved badly; they produced oil nicely for a short time, and then production fell off sharply, often failing to break even. In 1950, the cost of drilling and putting down 8000 feet (2,438.4 m) of steel casing, versus the low federally mandated price of $2.58/barrel, required a well to produce 50000 barrels (7,949.4 m³) just to break even. Local companies who had been skeptical of the Spraberry since the beginning of the boom did not suffer the losses of the outsiders who had come in to profit on the huge new field. Even the professional geologists could not agree on what was wrong: in October, 1951, a convention in Midland of hundreds of engineers and petroleum geologists reached no consensus on the issues with the field, although the peculiar and irregularly fractured nature of the oil-bearing rocks seemed to be a large part of the problem. In May 1952, there were over 1,630 wells in the Midland basin, most recently drilled, but local enthusiasm had ended. In the following years, each operator developed their own methods of dealing with the unusual reservoir, and began to employ a technique known as "hydrofracturing" – forcing water down wells at extreme pressure, causing the rocks to fracture further, resulting in increased oil flow. This was moderately successful, and development of the Spraberry continued, albeit with greatly diminished expectations for massive output. Yet another method of fracturing the rocks to increase production was to pump a mixture of soap and kerosene, followed by a coarse-grained sand, also under intense pressure.
During the initial boom period the Spraberry promoters carried out an aggressive campaign to bring in outside investment, making exorbitant claims of the potential of the reservoir, with its vast reserves of oil and easy profit. As every well drilled into the Spraberry Sands anywhere in the Midland Basin found oil, at least initially, it seemed at first that their claims were not completely without merit. Yet their tactics were not subtle: one group of promoters from Los Angeles brought in a group of Hollywood models, and had these women photographed on the drilling rigs, working the equipment in the nude.
Using the normal 40 acres (161,874.4 m²) spacing employed elsewhere in West Texas proved impossible on the Spraberry; wells that close competed against each other, as yields per-acre from the difficult reservoir were dropping into the hundreds, rather than the expected thousands of barrels. Oil companies resorted to the unusual step of asking the Railroad Commission of Texas
, the regulatory body which decided on well spacing and production quota, to require 80 acres (323,748.8 m²), and then even 160 acre (0.6474976 km²) spacing to allow each drilling site to be profitable. Many of the initial wells were abandoned in the next few years as they ran out of oil; modern enhanced recovery techniques, such as carbon dioxide injection, were not yet available.
For a period in the 1950s the abundant natural gas in the reservoir was simply flared off – burned above the wellhead – since no recovery infrastructure existed. Steel was expensive, transport costs high, and profit margins from the field were too low to allow the development of the sort of gas pipelines that exist in most modern oil fields. Aircraft pilots reported that hundreds of square miles of west Texas were lit at night from the fires of thousands of gas flares, and the people in Midland reported seeing what appeared to be a false sunrise in the east shortly after each sunset. In 1953 the Railroad Commission prohibited the wasteful practice, shutting down all wells in the field until a recovery system could be built. After a series of lawsuits and court battles, the Railroad Commission backed down, compromising with the operators by allowing them a set number of days per month during which they could pump oil and flare gas. The overall gas reserves of the field were estimated to be over two trillion cubic feet; during the peak of the early 1950s gas-flaring, over 220 million cufts (6,229,706.3 m³) per day were burned.
The field grew in the 1960s with the annexation of several adjacent oil pools, and overall production increased with the implementation of enhanced recovery
technologies, such as waterflooding. In the 1970s, as the price of oil went up, drilling and production proceeded; while Spraberry wells were never abundant producers, during periods of high prices they could provide dependable profits for oil companies, and the local economy entered its strongest period. In the 21st century, newer technologies such as carbon dioxide flooding have been used to increase production. Even with these advances, the Spraberry retains about 90% of its original calculated reserves, largely due to the difficulty of recovery. As of 2009, there were approximately 9,000 active wells in the Spraberry Trend.
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, covering large parts of six counties, and having a total area of approximately 2500 square miles (6,475 km²). It is named for Abner Spraberry, the Dawson County farmer who owned the land containing the 1943 discovery well. The Spraberry Trend is itself part of a larger oil-producing region known as the Spraberry-Dean Play, within the Midland Basin. Discovery and development of the field began the postwar economic boom in the nearby city of Midland
Midland, Texas
Midland is a city in and the county seat of Midland County, Texas, United States, on the Southern Plains of the state's western area. A small portion of the city extends into Martin County. As of 2010, the population of Midland was 111,147. It is the principal city of the Midland, Texas...
in the early 1950s. The oil in the Spraberry, however, proved difficult to recover. After about three years of enthusiastic drilling, during which most of the initially promising wells showed precipitous and mysterious production declines, the area was dubbed "the world's largest unrecoverable oil reserve."
In 2007, the U.S. Department of Energy ranked The Spraberry Trend third in the United States by total proved reserves, and seventh in total production. Estimated reserves for the entire Spraberry-Dean unit exceed 10 Goilbbl, and by the end of 1994 the field had reported a total production of 924 Moilbbl.
Setting
The Spraberry Trend covers a large area – around 2500 square miles (6,475 km²) – and includes portions of two Texas geographical regions, the Llano EstacadoLlano Estacado
Llano Estacado , commonly known as the Staked Plains, is a region in the Southwestern United States that encompasses parts of eastern New Mexico and northwestern Texas, including the South Plains and parts of the Texas Panhandle...
and the Edwards Plateau
Edwards Plateau
The Edwards Plateau is a region of west-central Texas which is bounded by the Balcones Fault to the south and east, the Llano Uplift and the Llano Estacado to the north, and the Pecos River and Chihuahuan Desert to the west. San Angelo, Austin, San Antonio and Del Rio roughly outline the area...
. As most often defined, the Spraberry includes portions of Irion, Reagan
Reagan County, Texas
Reagan County is a county located on the Edwards Plateau in the U.S. state of Texas. In 2000, its population was 3,326. The seat of the county is Big Lake. It is named in honor of John Henninger Reagan , who served as postmaster general of the Confederate States of America and also as a U.S....
, Upton
Upton County, Texas
Upton County is a county located on the Edwards Plateau in the U.S. state of Texas. In 2000, its population was 3,404. Its county seat is Rankin. The county is named for two brothers: John C. and William F. Upton, both Colonels in the Confederate army....
, Glasscock, Midland, and Martin Counties, although the underlying geologic unit also touches Dawson, Crockett, and Andrews Counties. Elevations are generally between 2,500 and 3000 feet (914.4 m) above sea level, and the terrain varies from flat to rolling, with occasional canyons, known locally as "draws", cutting through the plateau. Drainage is to the east, via the Concho River
Concho River
The Concho River is a river in the U.S. state of Texas. It has three primary feeds: the North, Middle, and South Concho rivers. The North Concho River is the longest fork, starting in Howard County and traveling southeast for until merging with the South and Middle forks near Goodfellow Air...
to the Colorado River
Colorado River (Texas)
The Colorado River is a river that runs through the U.S. state of Texas; it should not be confused with the much longer Colorado River which flows from Colorado into the Gulf of California....
. The climate is semi-arid
Semi-arid
A semi-arid climate or steppe climate describes climatic regions that receive precipitation below potential evapotranspiration, but not extremely...
. Native vegetation includes scrub and grasslands, with trees such as cottonwoods along the watercourses.
Aside from activities associated with oil production, transport, and storage, predominant land use in the area includes ranching and farming.
Geology
All of the Spraberry Trend oil fields produce from a single enormous sedimentary unit known as the Spraberry Sand, which consists of complexly mixed fine sandstoneSandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
and calcareous or silicate mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
and siltstone
Siltstone
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...
, deposited in a deep water environment distinguished by channel systems and their associated submarine fans, all of Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
age. The sands are interbedded with shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
s, and typically pinch-out updip. Unlike many of the oil-bearing rocks of West Texas, however, the Spraberry Sands have very low porosity
Porosity
Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0–1, or as a percentage between 0–100%...
and permeability, both of which hamper oil recovery. The rocks are naturally fractured, further complicating hydrocarbon flow. Oil has accumulated in stratigraphic traps, migrating upward from source rocks until encountering impermeable barriers, either in the internal shaly members or the overlying impermeable formation.
Shaly rocks make up a total of 87% of the Spraberry, with the oil-bearing sands and siltstones present sometimes in thin layers between them. The best-producing zone is at an average depth of 6800 feet (2,072.6 m) across the entire region, which is about 150 miles (241.4 km) long by 70 wide.
History
The first well drilled into the formation was by Seaboard Oil Company in 1943, on land owned by farmer Abner Spraberry in Dawson County. While the well bore showed an oil-bearing unit had been found, and hence received Spraberry's name, it did not produce commercial quantities of oil. That changed in 1949, when the same company drilled well Lee 2-D, which produced 319 oilbbl/d – hardly a spectacular discovery, but enough to pique the interest of numerous independent operators looking for opportunity around Midland. In 1950 and 1951 several other independent oil companies drilled productive wells into the same formation, separated by great distances, establishing that the formation was at least 150 miles (241.4 km) long, and beginning a frenzy of drilling in the region surrounding Midland.Unfortunately for most of the speculators, investors, and outside independent oil companies, most of the newly drilled wells behaved badly; they produced oil nicely for a short time, and then production fell off sharply, often failing to break even. In 1950, the cost of drilling and putting down 8000 feet (2,438.4 m) of steel casing, versus the low federally mandated price of $2.58/barrel, required a well to produce 50000 barrels (7,949.4 m³) just to break even. Local companies who had been skeptical of the Spraberry since the beginning of the boom did not suffer the losses of the outsiders who had come in to profit on the huge new field. Even the professional geologists could not agree on what was wrong: in October, 1951, a convention in Midland of hundreds of engineers and petroleum geologists reached no consensus on the issues with the field, although the peculiar and irregularly fractured nature of the oil-bearing rocks seemed to be a large part of the problem. In May 1952, there were over 1,630 wells in the Midland basin, most recently drilled, but local enthusiasm had ended. In the following years, each operator developed their own methods of dealing with the unusual reservoir, and began to employ a technique known as "hydrofracturing" – forcing water down wells at extreme pressure, causing the rocks to fracture further, resulting in increased oil flow. This was moderately successful, and development of the Spraberry continued, albeit with greatly diminished expectations for massive output. Yet another method of fracturing the rocks to increase production was to pump a mixture of soap and kerosene, followed by a coarse-grained sand, also under intense pressure.
During the initial boom period the Spraberry promoters carried out an aggressive campaign to bring in outside investment, making exorbitant claims of the potential of the reservoir, with its vast reserves of oil and easy profit. As every well drilled into the Spraberry Sands anywhere in the Midland Basin found oil, at least initially, it seemed at first that their claims were not completely without merit. Yet their tactics were not subtle: one group of promoters from Los Angeles brought in a group of Hollywood models, and had these women photographed on the drilling rigs, working the equipment in the nude.
Using the normal 40 acres (161,874.4 m²) spacing employed elsewhere in West Texas proved impossible on the Spraberry; wells that close competed against each other, as yields per-acre from the difficult reservoir were dropping into the hundreds, rather than the expected thousands of barrels. Oil companies resorted to the unusual step of asking the Railroad Commission of Texas
Railroad Commission of Texas
The Railroad Commission of Texas is the state agency that regulates the oil and gas industry, gas utilities, pipeline safety, safety in the liquefied petroleum gas industry, and surface coal and uranium mining .Established by the Texas Legislature in 1891, it is the state's oldest regulatory...
, the regulatory body which decided on well spacing and production quota, to require 80 acres (323,748.8 m²), and then even 160 acre (0.6474976 km²) spacing to allow each drilling site to be profitable. Many of the initial wells were abandoned in the next few years as they ran out of oil; modern enhanced recovery techniques, such as carbon dioxide injection, were not yet available.
For a period in the 1950s the abundant natural gas in the reservoir was simply flared off – burned above the wellhead – since no recovery infrastructure existed. Steel was expensive, transport costs high, and profit margins from the field were too low to allow the development of the sort of gas pipelines that exist in most modern oil fields. Aircraft pilots reported that hundreds of square miles of west Texas were lit at night from the fires of thousands of gas flares, and the people in Midland reported seeing what appeared to be a false sunrise in the east shortly after each sunset. In 1953 the Railroad Commission prohibited the wasteful practice, shutting down all wells in the field until a recovery system could be built. After a series of lawsuits and court battles, the Railroad Commission backed down, compromising with the operators by allowing them a set number of days per month during which they could pump oil and flare gas. The overall gas reserves of the field were estimated to be over two trillion cubic feet; during the peak of the early 1950s gas-flaring, over 220 million cufts (6,229,706.3 m³) per day were burned.
The field grew in the 1960s with the annexation of several adjacent oil pools, and overall production increased with the implementation of enhanced recovery
Enhanced oil recovery
Enhanced Oil Recovery is a generic term for techniques for increasing the amount of crude oil that can be extracted from an oil field...
technologies, such as waterflooding. In the 1970s, as the price of oil went up, drilling and production proceeded; while Spraberry wells were never abundant producers, during periods of high prices they could provide dependable profits for oil companies, and the local economy entered its strongest period. In the 21st century, newer technologies such as carbon dioxide flooding have been used to increase production. Even with these advances, the Spraberry retains about 90% of its original calculated reserves, largely due to the difficulty of recovery. As of 2009, there were approximately 9,000 active wells in the Spraberry Trend.