CNPC＇s Future Exploration Targets for Giant Gas Fields

OIL and GAS RESOURCESCNPC'S Future ExplorationTargets for Giant Gas FieldsFan Wenke', Zhang Fudong, Wang Zongli, Yang Dong Yang Shen(1. Petro China Exploration and Production Company; 2. Langfang Brach of PetroChina Petroleum Explorationand Development Research Institute)The 2 1st century is regarded as an era of natural gas basin and vocalic stonesfor the petroleum industry. That is one of the reasons whyCNPC had been taking a series of measures during the Discovered and confirmed a batch of targets forEleventh-Five-Year-Plan(EFYP) period to strengthen its future gas explorationsexploration for oil gas, especially for gas. As a result, During the EFYP period, CNPC has made progressCNPC quickly entered a new phase of gas development. in its gas exploration in such basins as Erdos, SichuanIt harvested many strategic achievements of high quality Tarim, Sonliang and Juggar. It discovered and confirmeduntapped gas reserves, therefore was able to realize a 3 areas with gas reserves of more than 1000 billion cubicsustainable and quick growth in natural gas reserves. meters (namely they are the Sulige, the Kuche, and theMeanwhile, the company managed to probe deeper into Xujiahe), and 4 areas with gas reserves ranging betweenthe possible areas for locating giant gas fields so as to 300-500 million cubic meters in deep Songliao basinlay down a sound foundation for the future development. central Tarim basin, and the east part as well as Ludong-During the EFYP period, CNPC confirmed six basins for Wucaiwan of Erdos. The Longgang area in Sichuan basingas exploration: Erdos, Sichuan, Tarim, Qaidam, Songliao also contains gas reserves of certain scaleand Juggar. Analysis indicates that large area of sandstone, The Sulige gas field, the biggest gas field in themarine carbonate, foreland basins as well as volcanic gas country, was discovered before the year of 2004 and withreservoirs in these basins are the key domains for future an accumulative measured gas in place of 0.6x10m'.Thegas discoveries. Bio-gas and unconventional gas are the field was developed effectively as the company introducedhope for China's future gas supplythe market mechanism into the field in 2005. In 2006CNPC drafted the overall plan for adding 2x10"mAdvancement in gas exploration during the measured reserves to the company's gas reserve base byEFYP periodthe end of the EFYP period and then initiated large scaleA new phase for a quick natural gas reserve growth exploration in adjacent areas around the field. From 2007During the period, CNPC maintained a positive growth to 2010, the company had been mainly focused on themomentum of the last five-year plan period(see Fig. 1). exploration of the block East-I and the block West-IWith a measured gas in place of 2.14x10m' added to strengthened exploration in the block West-2 and the blockthe company's gas reserve base, CNPC gained an average East-2, while totally gave up the south part of the area. Asannual gas reserve growth of 0.42x10m, making the a result, an estimated total reserves of 2.8x10m'wereperiod the fastest growth time in Chinas oil and gas added to the comp!中国煤化工 producingindustry. The newly added reserves are mostly distributed area with reserves oCNMHGin large area of sandstone, marine carbonate, forelandThe Kela-2 gas field in the Kuche area of Tarim basiCHINA OIL GAS19No.2.2012OIL and GAS RESOURCES50004000300020001000nn口nFig 1 histogram showing the growth trend of CNPC's gas reserves(100 million cubic meters)was discovered in 1998, and in 1999, the well Dabei-I basin was a breakthrough for the company in 2003encountered gas and later evolved into a gas field. InIn 2005, CNPC confirmed the condensate reservoir in2001, the Dina gas field was established with the well the Formation. In 2006, breakthrough was made in theDina-2 being the discovering well. Since the year of 2006, exploration of Karst reservoirs in the Yingshan FormationCNPC had been focused on tackling the key technology of the Ordovician in the northern slope of the centralissues that constrain the exploration of the area. It Tarim basin through the well Tazhong-83 Since thenimproved the quality of seismic data and confirmed an the company carried out a thorough assessment of theassumption that the Kelasu structural belt is consisting of No I slope break and confirmed gas in place of nearlyfive layers. The company also implemented the vertical 0. 1x10"m through drilling such wells as the Tazhongdrilling technology to increase drilling speed and reduce 26, Tazhong-82, Tazhong-86 and Tazhong-45, amongengineering accidents. In 2007, the well Dabei-3 produced them the karst reservoirs penetrated by the well Tazhong-with high gas rate and led to the establishment of the 83, Zhonggu-8 and Zhonggu-43 offered measured gasflowed gas of high rate-a breakthrough in exploration of basin added 0.4x10"m of gas to the company's resen .?Dabei gas field. In the following year, the well Keshen-2 place of 0.3x10'm. During the EFYP period, the Tarimthe Keshen structure. From 2009 to 2010, the company base and is very much likely to become a gas supplyhad been working with its assessment of the Dabei gas source with a reserve of 500 billion cubic metersfield and its exploration of the Keshen structure. During The year of 2002 marked the breakthrough for volcanicthe EFYP period, CNPC had added a total gas in place gas reservoir exploration in deep Songliao basin whereof about 0.8x10"m to its reserve base. An area with the well Xusheng-l was drilled and encountered gassufficient gas supply is thought to be taking shape.Ever since then, CNPC had sped up its pace of exploringSandbodies in the Xujiahe Formation in Sichuan deep basin gas and realized leapfrog development forbasin is distributed widely and are considered a deep gas in northern Songliao basin. In 2005, gas flowedfavorite lithological condition for the formation of big out of the well Changsheng-I in the Changling fault andgas reservoirs Exploration breakthrough in the well initiated the exploration of deep gas from volcanic layersGuangan-2 in the basin in 2005 had led to a series of in the southern Songliang basin. In 2008, two wells indiscoveries of Guangan, Hechuan, Tongnan, and Anyue Yingtai fault depression also produced with high-rateas well areas with gas potential such as Yingshan and gas, further indicating gas potential of the deep volcanicShehong-Renshou. These achievements added nearly layers in the south part of the basin. Meanwhile, the deep0.9x10 m to the company's gas reserve basesandstone was中国煤化工 ve results: theThe well Tazhong-62 in the Lianglitage Formation of well XushengpCNMHGIt depressionthe Ordovician in the No I slope break of central Tarim (2009) and the well cnangsneng-lv In north slope of the20 CHINA OILOIL and GAS RESOURCESChangling fault depression(2010) flowed gas. During rate. The area showed features of wide-spreading, highthe period, the basin offered a reserve of more than abundance, and lithologic gas reservoirs and therefore0.5x10m', forming another gas supply source with more went through a large scale exploration afterwardsthan 500 billion cubic meters of gas reserveDuring the EFYP period, CNPC performed 3-D seismicc The Shengmu gas field in northern Erdos basin was survey over the most part of the area, and several wellsiscovered in 2007 when several wells were drilled in encountered industrial gas flow. The whole area offeredthe Taiyuan Formation. The field contains gas of more great potential for future reserve growththan 100 billion cubic meters, with gas in place of morethan 0.2x10"m. Also in 2007, two wells drilled in the The formation of six gas exploration targetssecond member of the Jiqushan Formation encountered CNPC has a gas resource of 303x10"m. By the endgas flow and the gas in place was estimated to be more of 2010, the company has an accumulative measuredthan 0.1x10 m. During the period, the Erdos basin gas in place 5.7x10m'. With an approved resourceadded 0.3x10m' gas to the companys reserve base and rate of 18.8%, the company is still at the early stage ofis capable of becoming one of the areas with gas reserve gas exploration. Seven basins(Erdos, Tarim, Sichuanscale ranging between 300 to 500 billion cubic meters. Qiantam, Songliao, Bohai Bay, Juggar) account forThe Wucaiwan gas field was discovered in the Ludong- 93%and 99% of the company's resource and measuredWucaiwan area of the Juggar basin in 1995 when the reserves in terms of the distribution of their resource andwell Cai-25 drilled into the Carboniferous layer. The well measured reservesDixi-10 drilled in 2004 in the Carboniferous layer led to As the company made giant progress in its gasthe establishment of the Dixi gas field. During the period exploration in Erdos, Tarim, Sichuan, Qiantam, Songliaoof 2005-2008, CNPC changed its exploration strategies Juggar, CNPC gradually formed six key gas explorationby focusing on the Carboniferous volcanic layers. This areas. By the end of 2010, the six areas contain anstrategic shift yielded very positive results. In 2006, accumulative gas in place of 5.5x10 m, accountingthe well Dixi-14 encountered high-rate gas flow. From for 96% of the company's accumulative measured gas2007 to 2008, five wells produced industrial flow from reserves. In 2010, CNPC's annual gas production wasthe Carboniferous layers and led to the establishment of 722x10 m. among which the six area offered 686x10'm'Kekameili gas field. During the EFYP period, the Juggar accounting for 95% of the totalbasin added nearly 0.2x10'm of gas in place to the Based on the exploration situation and resourcecompanys base and could be a gas supply source with distribution, CNPC further strengthened its gas exploration300 billion cubic meters of resourcesby initiating strategic disposition of reserve growth projectTwo sets of porous reservoirs were discovered in the by the end of 2007. Four years of implementation went onreef of the Permian Changxin Formation and the oolitic smoothly and laid down a good foundation for future gasbeach of the Triassic Feixianguan Formation in Longgang development of the companyarea with the well Longgang-l dried with high gas flow中国煤化工CNMHGCHINA OIL&GAS 21No.2.2012