Our Eagle Ford Shale assets have grown in significance to our operations, and we believe they will continue to be a growing portion of our portfolio in terms of oil production, oil reserves, and investment for several years. As part of the Meridian transaction in 2010, we acquired interests primarily in an area of Karnes County, Texas referred to as the Eagleville field. Our acreage position also includes portions of Goliad and DeWitt Counties. The Eagle Ford is a shale formation typically developed with horizontal wells, which produce a highly desirable mix of oil, natural gas, and natural gas liquids. We own an average 21-25% working interest in the field. The wells are primarily operated by Murphy Oil, which has a 120 well development program with the potential of down-spacing and has dedicated up to three drilling rigs, a fully-equipped hydraulic fracturing crew, and a coil tubing unit to the area for the next two years.
Our assets in Oklahoma are located in large oil fields with multiple pay zones at depths from less than 2,000 feet to 7,500 feet. The fields are located in the Sooner Trend area of the Anadarko Basin and were initially developed by Conoco, Texaco and Exxon. These assets are predominantly shallow-decline, long-lived oil fields originally drilled on uniform, 80-acre spacing and waterflooded to varying degrees. We own an 84% interest in the Lincoln North Unit which consists of approximately 80+ unit producing wells and six non-unit producing wells. We own an 89% interest in the Lincoln SE Unit, which consists of approximately 34 producing wells. We own an 88% interest in the East Hennessey Unit, which consists of approximately 62 producing wells.
Our activity in these fields include adding production from the Mississippian Lime formation by deepening existing wellbores and downspacing to 40 acre units, and by recompleting existing wellbores to other previously unexploited zones. This is a low-cost and low-risk strategy to increase oil production. Augmenting the economics of this strategy, we have already implemented technology for commingling oil production from multiple zones through a single tubing string. In addition, we are continuing to expand waterflooding in the East Hennessey Unit, and pilot-testing waterflooding in both Lincoln North and Lincoln Southeast.
Alta Mesa has three major areas of operation in South Louisiana, in fields originally developed by major oil companies, where we have working interests in over 60 producing wells and approximately 55,000 gross developed and undeveloped acres (~31,900 acres, net). These areas have multiple low-risk exploration and development targets, potential for exploiting substantial bypassed and overlooked oil pay zones, and opportunities to increase profitability through facilities de-bottlenecking, production enhancements and drilling.
Weeks Island Field . Weeks Island, located in Iberia Parish, contains some of our largest developed oil reserves. It is a historically-prolific oil field with 55 potential pay zones that are structurally trapped against a piercement salt dome, which we believe offer significant future opportunities for added production and reserves. The main field pay zones are characterized by high, stable production rates due to the predominant water-drive production mechanism and high-porosity sands. The field was discovered in 1945 by Shell and subsequently developed by Shell and Exxon. We acquired these properties in 2010 with our acquisition of Meridian, which had purchased them in 1998. We operate all of the wells in this field in which we have an interest. Since mid-2011 we have continuously employed one drilling rig and one completion rig in Weeks Island to exploit its potential for development through sidetracking, new drilling and recompletions. Additionally, Weeks Island oil sales prices are based on the Louisiana Light Sweet crude market price index, which has trended appreciably higher than the West Texas Intermediate index.
Our operations in this area are low-risk expansions of well-established natural gas fields through a consistent, integrated, multi-discipline technical approach to field re-development. Our principal assets in the area are the Urbana and Cold Springs fields, which are adjacent fields with similar geologic formations producing condensate-rich gas principally from the Wilcox formation. These fields were originally discovered in the 1940s and 1950s by major oil companies and were developed based on technology available at the time. The area is served by a robust pipeline and services infrastructure, and established local operators familiar with the fields, wells, and facilities. Wells are typically brought online relatively rapidly, and production is long-lived as we progressively produce from multiple pay zones. We have materially increased reserves and extended the life of these fields by utilizing modern well log and geochemical analyses, modern fracture stimulation techniques, and the integration of 3-D seismic for exploitation as well as exploration. Through Meridian we acquired an interest in over 26,508 net acres in the Austin Chalk and Wilcox formations, and have integrated these field operations with those of the nearby Urbana field
Urbana Field. We are the operator of the Urbana field, located in San Jacinto County, Texas and have an average 97% working interest in 25+ producing wells. Urbana is a known structure with multiple pay zones, and as many as 35 productive reservoirs from 7,200 feet to 11,600 feet deep. The liquids/oil to natural gas ratio of approximately 40 barrels per million cubic feet of natural gas from Urbana makes our wells economic even at low natural gas prices. We completed the first-ever 3-D survey over the Urbana structure in late 2009, which identified a new fault block and an additional horizon for future exploration.
Cold Springs and Cold Springs West Fields. The Cold Springs and Cold Springs West fields are located west of the Urbana field in San Jacinto County, Texas. We are the largest working interest owner with an average 75% working interest in 45+ producing wells. We acquired additional interests in 2011 and became the operator of the Cold Springs field.
The Cold Springs field is a known structure with multiple pay zones, similar to the Urbana field but we believe with larger and greater development and expansion potential. The liquids/oil to natural gas makeup of our production in this field is about 95 barrels per million cubic feet of natural gas, which makes our wells economic even at low natural gas prices. In 2010 and 2011, we extended Cold Springs with the annex called Cold Springs West, with nine new wells. The area is now contributing higher oil production. We acquired additional seismic data in 2011, which has allowed us to identify opportunities for shallow, relatively inexpensive drilling and recompletion activity.
Our Hilltop Field, acquired in 2009, is our largest natural gas asset due to the reserves in the Deep Bossier and Knowles formations. The field has been significantly developed in the Deep Bossier formation, a prolific producer of primarily dry natural gas which occurs at 15,000-20,000 feet. Our interests here, which are operated primarily by EnCana and Gastar, have increased from 30 to over 60 producing wells. Although the Deep Bossier has potential for additional development, we, together with other operators, have redirected our near-term focus to other more liquids-rich zones. The decrease in production reflects a decrease in continued Deep Bossier drilling as well as natural decline. We plan to target the Woodbine and Austin Chalk formations for oil exploration using horizontal drilling. These formations are located at a depth of approximately 7,000 feet in the Hilltop area, above the Deep Bossier and Knowles formations. The formations have historically been productive of oil in this area. Other shallower formations in the area that we believe have oil potential include the Pettet, James Lime, Glen Rose, and Buda formations. It is possible that the acreage that we believe is prospective in each of these formations may change, perhaps materially, as additional exploration and discovery efforts are conducted in these areas. Deeper formations that we believe have natural gas potential include the Knowles Lime, Bossier Shale, and Travis Peak. We have a large, contiguous acreage position in the Hilltop and adjacent Amoruso fields in Leon and Robertson Counties, Texas, of approximately 50,000 gross developed and undeveloped acres (~17,000 acres, net). EnCana is the primary operator, managing approximately two-thirds of our wells, with Gastar operating the remainder, and Alta Mesa operating one new well. Our operating agreements with EnCana and Gastar allow us substantial input related to operations and control of our capital expenditures, including provisions that permit us to either propose or non-consent individual wells. Our interests in this area include approximately 58 producing wells.
Hydraulic Fracturing: Safe Oil and Natural Gas Extraction