A New Gas Source for the West-East Gas Pipeline — Dina-2 Gas Field put into production

On June 28, 2009, Dina-2 Gas Field was put into production, which will annually supply 5 billion cubic meters of natural gas to the West-East Gas Pipeline.

Located in Kuche County and Luntai County in the south of Xinjiang Uygur Autonomous Region, or geologically in Kuche depression of the Tarim Basin, Dina-2 is an abnormally high pressure deep condensate gas field. On April 29, 2001, well Dina-2, drilled at Dina-2 structure in the east section of Qiulitage anticline in the east of Kuche depression, obtained a high yield oil and gas flow, with daily output of 2.18 million cubic meters of natural gas and 131 cubic meters of gas condensate from the Eogene system during formation testing, marking the discovery of Dina-2 Gas Field. The field has a proven gas in place volume of 175.22 billion cubic meters and gas condensate reserves of 13.39 million tons, making it by far China's largest condensate gas field.

Construction of Dina-2 Gas Field commenced on March 26, 2008, and was completed in 15 months. Facilities including internal gas gathering and transportation pipeline network, central processing plant, and external oil and gas transportation pipelines have been built. A total of 33 wells are designed to be drilled in the gas field, 28 among which are production wells. The gas processing plant is designed to process 5 billion cubic meters of natural gas and 560,000 tons of gas condensate, or 4.5 million tons of oil equivalent every year.

Considering the characteristics of condensate gas reservoirs, CNPC studies the development theory and model, and key development technologies for this kind of gas reservoir.

Dina-2 Gas Field, together with Yaha, Kela-2 and Yingmaili gas fields, will enable Tarim Oilfield's to produce over 20 billion cubic meters natural gas a year, ensuring stable supply to the West-East Gas Pipeline.

We are striving to build Dina-2 into "a green giant gas field". During the development of Dina-2 Gas Field, dump energy and natural pressure at the well heads have made reasonable use to transport natural gas, so as to cut energy consumption and costs. Solidification technology is adopted to treat the waste mud and solid wastes in well drilling, so as to eliminate the impact on underground water. A sonic system is used for the first time for flaring to save energy and reduce emissions.

In the area of Dina-2 Gas Field, there grows Ephedra which is of high medical value and windbreak and sand-fixation function. During the planning and construction of the gas field, we tried to keep away from the growing area of these plants, and minimize mechanical operation area to leave as much growing space as possible for Ephedra, tamarix ramosissima and diversifolious poplar.

Condensate gas resources in the Tarim Basin

Condensate gas reservoir is an important type of hydrocarbon accumulation between oil and gas reservoirs. In the original formation conditions, condensate gas is in the form of gas, but when formation pressure becomes lower than dew point pressure, "retrograde condensation" happens to turn condensate gas into the form of both gas and liquid. Besides high quality natural gas, gas condensate can also be extracted from condensate gas reservoir, which is a valuable and premium raw material for petrochemicals like ethylene.

Tarim Basin is the largest sedimentary petroliferous basin in China, covering an area of 560,000 square kilometers. The latest oil and gas resource appraisal shows that the provable oil and gas reserve of the basin is 12.3 billion tons - 6 billion tons of oil and 8 trillion cubic meters of natural gas. Among the 8 trillion cubic meters of natural gas resources, a large portion is condensate gas. CNPC has proved 13 high pressure condensate gas fields including Yaha, Jilake, Yingmaili and Dina, bearing 70.55 million tons of gas condensate and 254.56 billion cubic meters of natural gas in place, accounting for 35% of the total proven natural gas in place in the Tarim Basin and 40% of the proven gas condensate in place in China. Among the five medium-large sized gas fields that supply gas to the West-East Gas Pipeline, four are high pressure condensate gas fields.

Development technology for high pressure condensate gas field
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Condensate gas reservoirs are difficult to develop due to complicated development mechanism and high technical requirements. Most of the condensate gas reservoirs proved in the Tarim Basin are buried 5,000m underground with formation pressures up to 50-120MPa, featuring very complicated fluid phase state variation, and multiple reservoir types. All these add world-class difficulties to the development of high pressure condensate gas fields in the Tarim Basin in terms of development model selection, surface process for high pressure gas injection, high pressure well completion techniques, and safe and efficient well drilling in complex formation conditions.

Considering the characteristics of condensate gas reservoirs, CNPC studies the development theory and model, and key development technologies for this kind of gas reservoir. We have established phase state calculation model for high wax content condensate gas and theoretical model for condensate gas well testing, developed seepage theory of condensate gas reservoir, and formed three development models, i.e. high pressure cyclic gas injection development for high pressure condensate gas reservoir, cyclic gas injection development in the middle and late depletion period, and development by natural energy. Additionally, we have also developed design technology for integrated high pressure gas gathering, processing and injection system, high pressure cyclic gas injection technology, and well drilling and completion technology under complex formation conditions.

Tarim Oil Province

In the southern part of the Xinjiang
Uygur Autonomous Region, Tarim Oil and Gas Province is located in the Tarim Basin, China's largest oil and gas-bearing basin.