iptc16772-地震数据驱动致密气岩石物理分析

Copyright 2013, International Petroleum Technology Conference This paper was prepared for presentation at the International Petroleum Technology Conference held in Beijing, China, 26–28 March 2013. This paper was selected for presentation by an IPTC Programme Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the International Petroleum Technology Conference and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the International Petroleum Technology Conference, its officers, or members. Papers presented at IPTC are subject to publication review by Sponsor Society Committees of IPTC. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the International Petroleum Technology Conference is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, IPTC, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax +1-972-952-9435
ቤተ መጻሕፍቲ ባይዱ
Abstract Pore fluids prediction using seismic data is seldom covered in most considerable discussion in tight gas, although more interests are focused on fractures and sweet spots. Some theories based on homogeneous high porosity and permeability rocks have been widely investigated. Unfortunately, there seems to be no models published can properly describe the nonlinear relationship between saturation and P wave velocity at seismic frequency in tight reservoir, and low frequency experimental data are still scarce. Gases always tend to gather at upper pore spaces in reservoir, resulting in saturation variation with depth due to interaction principle between buoyancy and capillary pressure. This law hence encourages us to probe into partial saturation related elastic properties through seismic data mining incorporating with experimental and logging data to indicate fluids. Through various gas intervals oriented P wave-‘saturation’ data collections extracted from seismic data, new nonlinear relations are discovered, which indicate coexistence of patchy and homogeneous fluids effects, and cannot be properly explained by published models. Motivated by the complex relations of Vp-Sw at seismic frequency, a modified White’s model is proposed to explain partial saturation effects in tight rocks, and updated rock physics models match the real seismic data quite well. Case study of tight gas exploration in a Triassic basin in southwest China shows that seismic data-driven models are helpful means to reduce uncertainly in seismic interpretation and have improved the success rate of drilling by 20%. Introduction Tight gas, which is widely distributed in over 70 basins and shares a large portion of unconventional resources, has attracted extensive interests on exploration and production in recent 10 years. According to the latest resource evaluation results, the potential resources of tight gas in China goes up to 947TCF, and had contributed 39% to the proved reserve by the end of year 2011 and 25% to the gas production in the year 2011 (Zhang et al., 2011; Yang et al., 2011). Prospectively, tight gas might become one primary gas resources in the coming 10 to 20 years. The term tight gas and issues discussed in this paper mainly refers to the low permeability tight sandstone, although there are some other tight gases produced from carbonates, coal beds and shale. By the suggested definition by Holditch (2006), tight gas reservoir can not meet economical requirements unless using enhanced treatments like fracturing, horizontal wells or multilateral wells. Actually, most papers were focused on engineering purpose, while potential technical contributions of lowering exploration risks had seldom been taken into concern except seeking sweet spots, and this unfortunately resulted in relatively poor understanding of geology, rock properties, models, and related seismic responses of tight gas, which was vital to seismic interpretation. In this paper, the authors brought an idea of seismic data mining, which might help to understand those elastic properties at low frequency, and built up quantitative models mainly driven by seismic data for pore fluids prediction and saturation estimation. The main purpose of the work was to find out an effective way to verify those seismically interpreted sweet spots and hence to lower drilling risks.