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Coal seam gas associated water production in Queensland: Actual vs predicted
Gas Science and Engineering ( IF 5.285 ) Pub Date : 2018-02-17
J.R. Underschultz, S. Vink, A. Garnett

Coal Seam Gas (CSG) development in Queensland is currently going through a transition from less than 300 billion cubic feet/year (∼315 PetaJoules/year (PJ/yr)) for domestic consumption to ∼1400 bcf/yr (nearly 1500 PJ/yr) by about 2019 driven by additional Liquid Natural Gas (LNG) export contracts. Prior to this ramp up in production, industry, government and academia have been forecasting not only gas but associated water production (produced water) for the various purposes of financial investment decisions and field development planning, prudent governance and regulatory planning, and estimation of potential environmental impacts for planning management, monitoring and mitigation strategies. During the course of resource development, prediction methodologies and model sophistication has varied greatly as more data becomes available and uncertainty is reduced. In Queensland, now that all 6 LNG trains are running and at various stages of ramping up to full production, there is a substantial and growing data inventory to history match numerical models and improve forward forecasting.

We review the historical forecasting of CSG water production in Queensland leading up to the development and operation of CSG to LNG export, and compare that to the current actual produced volumes now that the projects have come on stream. The latest available measured produced water from CSG development (December 2016) equates to ∼60.5Giga Litres/year (GL/yr) with combined operator forecasts defining a peak projected to occur for about 10 years at 70–80 GL/yr. When this is converted to cumulative water volumes over the life of the industry (based on combined operator forecasts), just over 1700 GL of water is expected to ultimately be produced. Current estimates of water and salt production in Queensland are about 25% of those made by government and academia prior to the expansion of CSG to LNG export and ∼70% of the 2010–11 industry estimates. We show that this discrepancy can be attributable to a combination of the following factors:

1.

Gas industry conservatism (over-estimation) driven by the bias to reduce project risk and achieve gas delivery targets;

2.

Government conservatism driven by a bias for prudent forecasting i.e. to assure that a credible worst case can still be managed within the regulatory framework;

3.

Academia conservatism driven by a bias for understanding worse case scenarios of environmental impact;

4.

The use of numerical models for basin scale impact assessment that do not take account of near-well multi-phase flow characteristics of saturation and relative permeability; and

5.

A systemic underestimation of the cumulative effects on depressurization of the coal resource where one operator's asset requires less water production to reach target reservoir pressures due to neighbouring operator production. This is mainly because each operator only has access to its own development plans.



中文翻译:

昆士兰州与煤层气相关的产水量:实际值与预测值

昆士兰州的煤层气(CSG)开发目前正经历着从不到3000亿立方英尺/年(约315皮焦耳/年(PJ /年))的国内消费过渡到约1400 bcf /年(约1500 PJ /年)的转变。年)到2019年左右,这是由额外的液态天然气(LNG)出口合同推动的。在产量大幅度提高之前,工业,政府和学术界一直在预测各种目的,不仅用于天然气,而且用于金融投资决策和油田开发计划,审慎的治理和监管计划以及对潜在潜力的估计等各种目的的相关水产量(产出水)对规划管理,监控和缓解策略的环境影响。在资源开发过程中,随着更多数据的可用和不确定性的降低,预测方法和模型的复杂性也发生了很大变化。在昆士兰州,现在所有6台LNG列车都在运行,并且处于逐步提高到全面生产的各个阶段,因此存在大量且不断增长的数据库存,以进行历史匹配数值模型并改善前瞻性预测。

我们回顾了昆士兰州CSG产水到LNG出口CSG的开发和运营之前的历史预测,并将这些项目与目前的实际产量进行了比较,因为这些项目已经投产。CSG开发(2016年12月)的最新可用测得出的产水量约为60.5千兆升/年(GL /年),结合运营商的预测确定了预计在70-80 GL / yr的十年内将出现一个峰值。当将其转换为整个行业生命周期内的累积水量时(根据运营商的综合预测),最终最终将生产出超过1700 GL的水。昆士兰州目前对水和盐产量的估计约为政府和学术界在将CSG扩大到LNG出口之前做出的估计的25%,约占2010-11年行业估计的70%。

1。

降低项目风险和实现天然气交付目标的偏见推动了天然气行业的保守性(高估);

2。

出于对审慎预测的偏见而驱动的政府保守主义,即确保仍然可以在监管框架内管理最坏的情况;

3。

出于对环境影响的更坏情况的理解而产生的偏见所驱动的学术保守主义;

4,

在不考虑饱和度和相对渗透率的近井多相流特征的情况下,将数值模型用于流域规模影响评估;和

5,

系统地低估了对煤炭资源降压的累积影响,其中一个运营商的资产由于邻国运营商的生产而需要较少的水产量才能达到目标储层压力。这主要是因为每个运营商只能访问自己的开发计划。

更新日期:2018-02-17
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