Pioneers of Jamaican geology and the Jamaica Group of the Geologists’ Association (1955–1959)

The formation of a geological society in Jamaica was dependent upon attaining a sufficient number of interested geologists on the island. Although the earliest study of Jamaican geology dated to the 1820s (De la Beche), few major geologists worked on the island in the 19th (Barrett, Sawkins, Hill) and early 20th centuries (Matley, Trechmann). A ‘critical mass’ of geologists was only attained in the 1950s after foundation of the third Geological Survey of the island, when, for the first time, the island had a resident geological intelligentsia. The director, V.A. Zans (1904–1961), was a Latvian geologist appointed from a camp for displaced persons. His staff included L.J. Chubb (1887–1971), who popularised geology in Jamaica. Chubb and his colleagues devised a three part plan for geological education in Jamaica: high schools were encouraged to introduce geology as an examination subject; introduction of geology as a part of the Natural Sciences curriculum at the University College of the West Indies was supported; and a local geological society for both amateurs and professionals was established. This society, the Jamaica Group of the Geologists’ Association, was established in 1955 and was the only such overseas group ever founded; Chubb was elected President. The first field trip was led by Zans and A.D. Foster in November 1955. The Group was reformed as the independent Geological Society of Jamaica (GSJ) in late 1959, again with Chubb as the first President. The GSJ remembers the name of its first President in the prestigious L.J. Chubb Award.     

International Association of Hydrogeologists and China

Before 1985, there were a few Chinese participators for International Association of Hydrogeologists which founded in 1956. The Chinese team composed of senior hydrogeologists attended the 17th and 18th IAH congress in 1985. More and more Chinese delegates were present at the conferences since then. The IAH National Chapter of China was first established in 1987 and organized related activities continuously since that time. The IAH members in P.R. China increased in these years. IAH congresses have been hold in China twice. The 21th congress was held in Guilin City in October, 1988. The 34th congress was held in Beijing in October, 2006. The IAH China Chapter serves for all IAH members and other scientists promoting groundwater sciences in China. There were a lot of national conferences on Hydrogeology and Groundwater sciences held almost every year since 1987. Those national conferences associate with Commission on Hydrogeology, Geology Society of China in operation. Many Chinese IAH members were the editors and responsible for the Chinese translation for the abstract of Hydrogeology Journal. The Journal of Groundwater Science and Engineering is an international journal for the natural sciences. The sponsors are IAH China chapter, Institute of Hydrogeology and Environmental Geology, CAGS.     

Use of formation pressure test results over a hydrate interval for long-term production forecasting at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Implications of uncertainties

In the first part of this paper, the pressure and temperature measurements obtained using Schlumberger's Modular Formation Dynamics Tester (MDT) conducted on the C2 interval in the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well (Mount Elbert Well) are history matched, with the following three objectives: (i) to obtain a better understanding of hydrate decomposition and its reformation as conditions cross the p/T stability, (ii) to obtain formation properties (e.g., permeability) that are consistent with the measurements, and (iii) to explore the non-uniqueness in the history match; i.e., to explore the ranges of parameters that allow a reasonable match of the measured quantities. In the second part of this paper, long-term production performance is predicted, and the effect of the uncertain parameters on the predictions is demonstrated. The results are used to demonstrate the range of long-term production that may be expected, when a model is calibrated using the MDT data. Usefulness of short-term tests for long-term forecast prediction is then discussed.     

An iterative ensemble Kalman filter for reservoir engineering applications

The study has been focused on examining the usage and the applicability of ensemble Kalman filtering techniques to the history matching procedures. The ensemble Kalman filter (EnKF) is often applied nowadays to solving such a problem. Meanwhile, traditional EnKF requires assumption of the distribution’s normality. Besides, it is based on the linear update of the analysis equations. These facts may cause problems when filter is used in reservoir applications and result in sampling error. The situation becomes more problematic if the a priori information on the reservoir structure is poor and initial guess about the, e.g., permeability field is far from the actual one. The above circumstance explains a reason to perform some further research concerned with analyzing specific modification of the EnKF-based approach, namely, the iterative EnKF (IEnKF) scheme, which allows restarting the procedure with a new initial guess that is closer to the actual solution and, hence, requires less improvement by the algorithm while providing better estimation of the parameters. The paper presents some examples for which the IEnKF algorithm works better than traditional EnKF. The algorithms are compared while estimating the permeability field in relation to the two-phase, two-dimensional fluid flow model.     

Time-dependent Inversion of Surface Subsidence due to Dynamic Reservoir Compaction

We introduce a novel, time-dependent inversion scheme for resolving temporal reservoir pressure drop from surface subsidence observations (from leveling or GPS data, InSAR, tiltmeter monitoring) in a single procedure. The theory is able to accommodate both the absence of surface subsidence estimates at sites at one or more epochs as well as the introduction of new sites at any arbitrary epoch. Thus, all observation sites with measurements from at least two epochs are utilized. The method uses both the prior model covariance matrix and the data covariance matrix, which incorporates the spatial and temporal correlations between model parameters and data, respectively. The incorporation of the model covariance implicitly guarantees smoothness of the model estimate, while maintaining specific geological features like sharp boundaries. Taking these relations into account through the model covariance matrix enhances the influence of the data on the inverted model estimate. This leads to a better defined and interpretable model estimate. The time-dependent aspect of the method yields a better constrained model estimate and makes it possible to identify non-linear acceleration or delay in reservoir compaction. The method is validated by a synthetic case study based on an existing gas reservoir with a highly variable transmissibility at the free water level. The prior model covariance matrix is based on a Monte Carlo simulation of the geological uncertainty in the transmissibility.     

基于两京（都）制论证候风地动仪存在的合理性

张衡的候风地动仪是否真实存在,至今还是一个有争议的科学与历史问题。否定其最大的理由在于因历史记载产生的矛盾。依《后汉书·张衡传》记载,张衡于阳嘉元年（公元132年）建造候风地动仪,而其卒于永和四年（公元139年）。在此期间,《后汉书》只记载过一次地震,即永和三年（公元138年）的甘肃陇西地震。一般认为候风地动仪记到的是此次地震。矛盾之处在于对公元138年甘肃陇西地震的历史记载出现不一致的情况：《后汉书·五行志》 记载当时京师“裂城廓,室屋坏,压杀人”,即在陇西地震的同时,京师也发生了破坏性的地震;而《后汉书·张衡传》却说“尝一龙机发而地不觉动,京师学者咸怪其无征”,记载的是在陇西地震发生时京师并无任何有感地震发生。由此,有人认为,在公元138年候风地动仪记录地震的同时京师就已经发生强烈有感地震了。人都有感,地震动仪记到也就不足为奇了。更进一步,由于历史记载出现矛盾,地动仪无出土实物,发明后很快遗失,因而就认为候风地动仪历史上并非真实存在,其存在性值得怀疑。本文针对这个记载矛盾做出另外一个解释,论证在东汉时有两个京师,一是长安,一是洛阳,京师震指的是长安,而候风地动仪放在河南洛阳。从而对历史记载中的矛盾有所解释,一定程度上肯定了候风地动仪存在的真实性。     

A method for automatic history matching of a compositional reservoir simulator with multipoint flux approximation

A method for history matching of an in-house petroleum reservoir compositional simulator with multipoint flux approximation is presented. This method is used for the estimation of unknown reservoir parameters, such as permeability and porosity, based on production data and inverted seismic data. The limited-memory Broyden–Fletcher–Goldfarb–Shanno method is employed for minimization of the objective function, which represents the difference between simulated and observed data. In this work, we present the key features of the algorithm for calculations of the gradients of the objective function based on adjoint variables. The test example shows that the method is applicable to cases with anisotropic permeability fields, multipoint flux approximation, and arbitrary fluid compositions.