南美桑托斯盆地深水区古拉绍-1井油气勘探发现及意义

Hydrocarbon discovery and its significance of Well Gulashao-1 in deepwater area of Santos Basin,South America

2021年,南美桑托斯盆地深水区风险探井古拉绍-1井获得重大原油发现,地层测试获得日产千吨高产油流,确定了巴西阿拉姆区块超大型油藏的勘探潜力,证实其具有规模商业开发前景。为了更好认识这一重大突破,在区域地质背景分析的基础上,结合油气勘探历程,对古拉绍-1井的构造-沉积背景、油气成藏条件以及油藏特点进行了详细分析。研究结果表明:①阿拉姆区块位于桑托斯盆地阿拉姆—乌拉普鲁(阿—乌)隆起带,与卢拉—苏格(卢—苏)隆起带的卢拉油田隔"湖"相望,具有相似的构造沉积背景;盆地中央大型古隆起为碳酸盐岩沉积提供了有利条件。②阿拉姆区块邻近主力生烃凹陷,油源充足。③继承性古隆起控制了湖相碳酸盐岩储层连片分布。④盐岩、盐上灰泥岩和泥岩对油藏形成了多重有效封盖。⑤盐下背斜圈闭规模大,为有利油气指向区。⑥古拉绍-1井油藏属于低CO_(2)、低H_(2)S中质油超压油藏。古拉绍-1井的成功钻探是巴西桑托斯盆地盐下核心区向外围区拓展取得的重大突破,是中国石油天然气集团有限公司(中国石油)坚持海外风险勘探的重大成功,是中国石油海外深水油气合作发展的又一成功实践,对巴西桑托斯盆地盐下油气勘探工作以及中国石油深水油气业务发展战略具有指导意义。

In 2021,a great breakthrough has been made in discovery of crude oil in the risk exploration well,i.e.,Well Gulashou-1,in deep water area of Santos Basin in South America;a daily production of thousands of tons of high-yield oil flows was obtained in the drill stem testing,thus determining a super large oil reservoir in the Alam block in Brazil and confirming its potential for large-scale commercial development.To better understand this major breakthrough,the tectonic-sedimentary environment,accumulation conditions and reservoir characteristics of Well Gulashao-1 were analyzed in detail based on the analysis of regional geological background,in combination with the exploration history.The results show as follows.(1)Alam block is located in the Alam-Uirapuru uplift belt of Santos Basin,facing with Lula oilfield in the Lula-Sugar uplift belt across a lake,and the both has a similar tectonic-sedimentary background.The large paleo-uplift in the center of the basin provides favorable conditions for carbonate sedimentation.(2)Alam block is adjacent to the main hydrocarbon generating sag with abundant oil sources.(3)The inherited paleo-uplift controls the contiguous distribution of lacustrine carbonate reservoirs.(4)Salt rocks,post-salt calcilutites and mudstones have formed multiple effective seals on the oil reservoir.(5)The pre-salt anticlinal trap is developed on a large scale,demonstrating a favorable migration direction of oil and gas.(6)The pool in Well Gulashao-1 is an overpressure reservoir,which produces medium crude oil with low CO_(2)and H_(2)S contents.The successful drilling of Well Gulashao-1 is a major breakthrough of oil exploration expanding from the pre-salt core area to the periphery in Santos Basin of Brazil.It is a major success achieved by PetroChina Company Limited(PetroChina)in adhering to overseas risk exploration and also a successful practice of overseas cooperation for deepwater oil and gas exploration in PetroChina.It is of guiding significance to the pre-salt oil and gas exploration in Santos Basin of Brazil and the development strategy of deepwater oil and gas business in PetroChina.