Changes

Production at Pinedale comes from the Lance Pool, which is nearly 6000 ft (1800 m) thick and consists of multiple stacked discontinuous Upper Cretaceous Lance and upper Mesaverde sandstones and siltstones that were predominantly deposited by fluvial processes and are encased in shales and mudstones. The reservoir rocks in Pinedale field occur at depths of about 8500 to 14,500 ft (2600–4400 m) and are tight with fairly low porosity (mostly <10%) and very low (micro-Darcy) permeability. The tight nature of these reservoir rocks makes it difficult for gas to move laterally and vertically for significant distances. As a result, it is necessary to conduct multistage hydraulic fracturing in all of the field's wells to create pathways for the gas to enter the wellbores at commercial rates.

Production at Pinedale comes from the Lance Pool, which is nearly 6000 ft (1800 m) thick and consists of multiple stacked discontinuous Upper Cretaceous Lance and upper Mesaverde sandstones and siltstones that were predominantly deposited by fluvial processes and are encased in shales and mudstones. The reservoir rocks in Pinedale field occur at depths of about 8500 to 14,500 ft (2600–4400 m) and are tight with fairly low porosity (mostly <10%) and very low (micro-Darcy) permeability. The tight nature of these reservoir rocks makes it difficult for gas to move laterally and vertically for significant distances. As a result, it is necessary to conduct multistage hydraulic fracturing in all of the field's wells to create pathways for the gas to enter the wellbores at commercial rates.

The tight nature of the reservoir rocks at Pinedale begs the question: “What makes Pinedale such a prolific natural gas field?” The field has some unique geologic characteristics. Production is reliant on a complex interplay of geologic factors, including structure, reservoir sandstone and siltstone thickness, porosity development, permeability, and reservoir pressure, which are in turn related to sedimentary facies, [[diagenesis]], water saturation and its control on relative permeability to gas, and possibly fracture size, density, and distribution. Added to these geologic parameters is the overprint of hydraulic fracture stimulation, which is done in every well. The Pinedale reservoir interval has about 1 billion cubic feet (bcf) of gas in place per acre. This high concentration of gas is in part due to the tremendous thickness (∼6000 ft, 1800 m) of the gas-saturated Lance and upper Mesaverde sections that comprise the Lance Pool. The gas volume is also enhanced by the overpressured character of the reservoir with pressures grading from about 0.57 psi per foot near the top of the Lance Pool up to 0.85 psi per foot near its base in parts of the field. In addition to the field's geologic characteristics, technological advances, particularly in drilling and hydraulic fracturing, have helped to release the gas trapped in the Lance Pool. Finally, high-density drilling, as dense as one well for five acres, has allowed for significantly improved recovery of natural gas from these tight reservoir rocks.

The tight nature of the reservoir rocks at Pinedale begs the question: “What makes Pinedale such a prolific natural gas field?” The field has some unique geologic characteristics. Production is reliant on a complex interplay of geologic factors, including structure, reservoir sandstone and siltstone thickness, porosity development, permeability, and reservoir pressure, which are in turn related to sedimentary facies, [[diagenesis]], water saturation and its control on relative permeability to gas, and possibly [[fracture]] size, density, and distribution. Added to these geologic parameters is the overprint of hydraulic fracture stimulation, which is done in every well. The Pinedale reservoir interval has about 1 billion cubic feet (bcf) of gas in place per acre. This high concentration of gas is in part due to the tremendous thickness (∼6000 ft, 1800 m) of the gas-saturated Lance and upper Mesaverde sections that comprise the Lance Pool. The gas volume is also enhanced by the overpressured character of the reservoir with pressures grading from about 0.57 psi per foot near the top of the Lance Pool up to 0.85 psi per foot near its base in parts of the field. In addition to the field's geologic characteristics, technological advances, particularly in drilling and hydraulic fracturing, have helped to release the gas trapped in the Lance Pool. Finally, high-density drilling, as dense as one well for five acres, has allowed for significantly improved recovery of natural gas from these tight reservoir rocks.

Pinedale field has had a long development history, which is described in detail in the following chapter by Kneller, Matheny, Albertus, and Riggs. The Pinedale anticline was first recognized from surface mapping in the early 1920s. The first well drilled on the anticline for hydrocarbons was the California Company's Government #1 drilled in 1939 and 1940. This well had gas shows in what is now recognized as the Lance Formation, but it tested at noncommercial rates and was eventually plugged and abandoned. Over the following 55 years, a number of other companies also attempted unsuccessfully to “crack the code” to produce economic quantities of natural gas from the micro-Darcy reservoir rocks within the anticline. However, it was not until the late 1990s when multistage hydraulic fracturing techniques that had been successfully employed in the nearby Jonah field, which lies just south of Pinedale field ([[:File:M107FG1.jpg|Figure 1]]), were brought onto the anticline that commercial production was established. These techniques finally allowed Pinedale operators to stimulate sufficient volumes of this extremely tight rock to allow gas to flow at commercial rates. Simply stated, it was technological advancements and innovative thinking that led to the commercialization of the Pinedale field.

Pinedale field has had a long development history, which is described in detail in the following chapter by Kneller, Matheny, Albertus, and Riggs. The Pinedale anticline was first recognized from surface mapping in the early 1920s. The first well drilled on the anticline for hydrocarbons was the California Company's Government #1 drilled in 1939 and 1940. This well had gas shows in what is now recognized as the Lance Formation, but it tested at noncommercial rates and was eventually plugged and abandoned. Over the following 55 years, a number of other companies also attempted unsuccessfully to “crack the code” to produce economic quantities of natural gas from the micro-Darcy reservoir rocks within the anticline. However, it was not until the late 1990s when multistage hydraulic fracturing techniques that had been successfully employed in the nearby Jonah field, which lies just south of Pinedale field ([[:File:M107FG1.jpg|Figure 1]]), were brought onto the anticline that commercial production was established. These techniques finally allowed Pinedale operators to stimulate sufficient volumes of this extremely tight rock to allow gas to flow at commercial rates. Simply stated, it was technological advancements and innovative thinking that led to the commercialization of the Pinedale field.