Natural gas is one of the important energy resource compairing with petroleum, coal and nuclear energy. Water dissolved natural gas accounts for one fourth of the natural gas production in Japan. In this paper, we present the geology and development technology of water dissolved natural gas in Japan, especially of Minami Kanto and Niigata gas fields. The situation of water dissolved natural gas development in the world is also presented.
The collapse resistance of oil country tubular goods has been a major concern for drilling engineers; i.e., the strong demand for high collapse resistant pipes for deep wells in 1970's, the question about collapse resistance under steam injection wells in the 1980's and, in these days, the collapse resistance of worn pipes and bent pipes in dog-leg wells. These collapse resistances vary with existence of axial load, reduction of material strength with temperature, or reduction of wall thickness at worn portion. However, the standard collapse test results of commercial pipes are always referenced as the base for estimating collapse resistances in various conditions. Thus the understanding of collapse properties of commercial pipes is very important. This paper deals with collapse resistance of commercial pipes under the uniaxial test condition. For this purpose, the influences of roundness error, eccentricity and residual stress on collapse resistance are discussed which are followed by the statistical analysis of collapse resistance in the light of those analyses. As a result, the following things are clarified. Firstly, rotary straightening develops residual stress in the pipe which degrades collapse resistance in the plastic collapse region. Secondly, FEM analysis is conducted which predicts reduction of collapse resistance due to roundness error and eccentricity. As an example, both 0.5% roundness error and 10% eccentricity reduce collapse resistance by 5%. Thirdly, less than 10% eccentricity and 0.3% roundness error seem to have no influence on collapse resistance for commercial pipes in practice. Finally, three experimental collapse resistance equations are obtained which are referred to regions of elastic collapse, plastic collapse and yield collapse. The commercially available pipe is characterized by significantly lowered collapse resistance in plastic regions affected by the circumferential residual stress.
The present paper proposes the algorithm for well log data analysis by use of neural network. The designated network is the layered network which consists of an input layer, one hidden layer and an output layer. The unit numbers of input layer and output layer are equal to well log curve to be inputted and the lithology to be outputted, respectively. The well log analysis procedure by use of neural network is divided into two stages, that is, training period and recognition period. During the training period, the initial weights which combine the units in each layer with those in the previous layer, are modified using the error back propagation algorithm so as to minimize the difference between the teacher's signal and the actual signal from output layer. The training period continues until the designated training counts are reached, or the residual between the teacher's signal and the actual signal from output layer becomes smaller than the designated value. After the completion of training period, the network is ready to analyze the new input data using the weight values. Aa a result of studies using the synthetic and the actual data, it was clarified that the proposed algorithm analyzed the well log data with good accuracy.
The main objectives of our present series of study are (1) selection of useful anaerobes for MEOR, (2) estimation of bacterial growth and their metabolic activities at reservoir conditions, (3) establishment of quantitative evaluation techniques of capabilities of anaerobes in improving oil recovery, and (4) investigation of recovery mechanisms. This paper describes methods and results of sampling and screening of enrichment anaerobic microbes, as a first stage of our fundamental studies on MEOR. Consequently, we selected possibly useful anaerobes and investigated their abilities. Samples were collected from formation waters, soils in oil fields, lakes and rivers. We obtained 22 kinds of microbes from these samples, and discovered 20 anaerobes among them through enrichment culture. The number of anaerobes selected for further experiment was 14, as a result of screening with the medium of 4% molasess with 0.8% Nutrient Broth at 30°C. Then, we investigated the effects of microscopic environment and presence of minerals on their activities. As a result, we obtained 6 useful anaerobes (3H, 4D, 6B, 7A, 8L, 9A) which had productivity of effective metabolites, though some other microbes were obstructed to grow under such conditions, which implied that both factors, inorganic salts and (porous) media, must be taken into account in screening. In addition, the microscopic observation showed that regarding some enrichment anaerobes, the kind of anaerobe having the predominant multiplication changed with media. Therefore, the isolation was carried out, and 2 isolated microbes from enrichment anaerobe 3H and 4 from 7A were obtained.
In part 1, the fundamentals of Microbial Enhanced Oil Recovery (MEOR) were introduced. Part 2 and 3 describe experiments, field trials and history of MEOR in detail. The introduction said that it is necessary to select useful microbes which have adaptabilities for reservoir conditions. Therefore, laboratory experiments which include sampling, screening and evaluating techniques of microbes are explained in a continued series. Microorganism samples are usually taken from reservoir or surface of oil fields, because reservoir-originated microbes have high adjustable abilities to target reservoir conditions. At the next step, only useful microbes for MEOR have to be selected through screening tests. The selected effective microbes are evaluated by their oil recovering abilities and then final candidates for field application are determined. These experimental techniques are generally presented in part 2.
Computer networking has become a critical tool for petroleum engineers. The Computer Sub-Committee of the Drilling Technology Committee has been investigating topics related to the effective utilization of computers and software. In this paper, how to access and what we can do with the Internet are described for beginners of the Internet.