Reservoir Block Research Articles

Effect of raised temperature on a stainless-steel surface by ambient atomic-force microscopy

We report images from atomic force microscopy (AFM) of a heated metallic surface performed under an ambient environment. The stainless steel surface was heated up to 121C, which is limited only by the capacitive heating element used (100W). We observed that the topography of the surface changes dramatically. It is found that at high temperatures, the surface appears flat compared with the presence of many round bumps observed on the same sample at room temperature when the ambient humidity is high. To the best of our knowledge, this is the first report on ambient AFM performed on a metallic surface above 100C.Most AFM systems adopt moving sample stages [1]. In this case, it is difficult to implement heavy heating heating elements and a heat reservoir block. For this experiment, the TAK3 from AT Corporation [2] is used. The sample stage is kept stationary and the heating element (the tip of a soldering iron) is fixed firmly on one side of a surface of the block using a screw.

Geostatistical Modeling of Gridblock Permeabilities for 3D Reservoir Simulators

Summary A geostatistical method is presented to determine the absolute horizontal and vertical effective permeabilities at the reservoir block scale from core support-scale values required for 3D reservoir flow simulations. The key element of the geostatistical model is the definition of block support-scale permeabilities as the spatial power average of core-support values over the volume of a reservoir gridblock. Block support-scale permeabilities are then found to be a function of the permeability variogram, the averaging volume, and a power-averaging constant, which is derived separately for horizontal and vertical flow with a numerical approach. The application of the proposed method requires that core-support values be available within each reservoir block. These values are generated with the technique of conditional simulation. This technique provides simulated values reproducing the actual core data at sampled locations and their statistical properties. The approach developed for the determination of permeability input to full-field simulators is demonstrated by an application to the Crystal Viking field "H" pool in Alberta.

Fault-Zone Seals in Offshore Trinidad Oil Fields

Hydrocarbon columns in Pliocene sands of offshore SE Trinidad occur in 3-way closure, primarily in the footwall of normal faults. Multiple reservoir sands and numerous fault blocks result in a large number of individual hydrocarbon accumulations. Fault-plane sections demonstrate that fault sealing is unrelated to juxtaposition of intercalated shales. These fault-zone capillary seals were studied by (1) inferring their fluid-flow properties from the pattern of trapped hydrocarbons and (2) direct examination and measurement of cored faults. Buoyancy pressures for hydrocarbon columns were calculated from fluid property data for each reservoir and fault block. Buoyancy pressures range widely, increasing nonlinearly with fault displacement and percent shale in the faulted section, but do not vary systematically with stratigraphic position or depth. Small-displacement faults observed in core are narrow zones of cataclasis within porous sandstone. Mercury injection tests indicate fault-zone displacement pressures that coincide with buoyancy pressures calculated for hydrocarbon columns sealed by large-displacement faults. The agreement between measured displacement pressures and calculated buoyancy pressures indicates that (1) the reservoirs are filled to their capacity, dictated by the displacement pressure of the fault zones, and (2) the fault-zone seals are primarily the product of deformation of the sands, with some enhancement by incorporation more » of argillaceous material into the fault zones. The observed relationship between fault displacement and calculated buoyancy pressure of the hydrocarbon columns implies that fault-zone continuity is a factor that needs to be assessed in fault-zone seal analysis. « less

Infrared absorption spectrometer for liquid semiconductors

An infrared absorption spectrometer for use with high-temperature liquids is described. The system has been used for liquid semiconductors at temperatures up to 550 °C having absorption edges as low as 0.3 eV. The optical cell consists of a thin (100–600 μm) gasket of graphite foil sandwiched between two optical flat windows and equipped with a fluid reservoir and heating block. This design allows the use of any optical windows chemically compatible with the sample. We have used several infrared windows to measure the optical absorption edge in selenium, selenium–tellurium, and selenium–thallium alloys down to 0.2 eV. This represents an improvement in the previous range of measurement which has been limited by the 0.5-eV cutoff of fused quartz cells.

Gravity and Capillarity Effects on Imbibition in Porous Media

Abstract This paper tries to assess the laboratory experiments used to scale gravity and capillarity-two active forces in the recovery process from matrix blocks in fissured reservoirs. We performed imbibition tests that show a great discrepancy among the scaled recovery curves corresponding to different block sizes. Several reasons tire considered to explain the failure of scaling rules:flow boundary conditions,local heterogeneities, andinstabilities in the water sweep. Introduction The numerical models used to forecast the behavior of fissured reservoirs now in service imply a knowledge of the particular recovery functions for matrix blocks. The aim is to provide the reservoir engineer with the simplest way w determine these recovery functions - by defining the conditions that must be respected so that laboratory tests on small samples may be used with scaling rules to simulate the behavior of a reservoir block. To keep the proper relationship between capillarity and gravity, Kyte suggested that gravity be artificially increased by carrying out the test in a centrifugal machine. This study tests the validity of this method. First we must examine from an analysis of the equations governing the problem, on which dimensionless groups (combinations of physical quantities) the recovery function of a block depends. Next, we must verify the theoretical conclusions of this analysis by experimenting on small-scale samples of a given shape and size, simulating the intensity of gravity by tests in a centrifugal machine. Then, we try to check the validity of scaling rules using cases in which experimental comparison can be achieved - imbibition experiments on samples geometrically similar, but of different sizes (diameters of 200, 70, and 40 mm). Results showed that these scaling rules were not valid. We then tried to isolate the phenomena that lead to the inadequacy of the conventional mathematical formulation by direct observation and by local measurement of saturation on the blocks during imbibition. THEORETICAL BASES Consider oil recovery from a cylindrical block of homogeneous, porous medium, initially saturated with oil and interstitial water, and then suddenly plunged into water. In the sample, the two plunged into water. In the sample, the two mechanisms of oil displacement by water (capillarity and gravity) are associated closely to contribute to production from a block, but their relative importance production from a block, but their relative importance depends on the dimensions of the block. Gravity becomes more important when the block is bigger, compared with capillarity. Theoretical study is based on the validity of the classical formulation of polyphasic flows in porous media on a macroscopic scale - that is, porous media on a macroscopic scale - that is, relative permeability and capillarity pressure. An analysis of the structure of the equations (Appendix) made it possible to reduce the parameters of the problem to a small number, such as problem to a small number, such as three dimensionless groups:(shape factor)(mobility ratio)(capillarity/gravity ratio)initial water saturationthe shape of the relative permeability curves and the reduced capillary pressure SPEJ P. 195

A Generalized Method for Making Optimal Estimates of Reservoir-Aquifer Parameters

Abstract This paper presents a new, faster method for predicting performance of reservoir aquifer systems predicting performance of reservoir aquifer systems and making optimal estimates of aquifer geometry, reservoir size, aquifer size, and reservoir-aquifer fluid conductivity. The method uses existing analytical solutions giving pressure-production performance of a radial or linear aquifer connected performance of a radial or linear aquifer connected to a reservoir with constant compressibility. The novelty of the method is the use of these solutions to predict behavior of a reservoir with compressibility changes. The method's accuracy was verified by comparing results with those calculated using a limite-difference simulator. The method is built into a computer program that uses an efficient optimization technique to estimate parameters. Results of application to a hypothetical gas reservoir and to an actual oil field are given. In the latter case, a comparison is made with results obtained using the Hurst-van Everdingen water influx calculation method Introduction Aquifers, linear or radial, surround many oil and gas reservoirs. Knowledge of the aquifer's strength is essential to predict future performance of a water-drive reservoir. Strength is influenced by geometric configuration, which may be difficult to determine. Often, geological interpretation suggests that the system is neither radial nor linear. Because it is possible that either aquifer shape might approximate the behavior of an actual system, it is frequently desirable to test both in a given problem. Several methods have been developed for predicting water influx into a reservoir. Of these, predicting water influx into a reservoir. Of these, Hurst's is closest to the method presented here. Hurst used the Laplace transformation to convert standard material balance equations for water-drive reservoirs into a form giving pressure explicitly as a function of other reservoir parameters. To apply his method for predicting reservoir pressure change, it is necessary to approximate all pressure-dependent functions as linear functions of pressure. Hurst gave no indication of the range of applicability of such an approximation and provided no convenient means for updating the approximations. This study develops an improved method for estimating groups of parameters that control behavior of a reservoir-aquifer system. The system is modeled as a single, homogeneous reservoir block with an active (radial or linear) aquifer. The steps taken to develop the method axe given and then its application to two practical field problems is shown. DEVELOPMENT OF METHOD This section presents the steps taken in developing the method. For each step, the main thrust of the work conducted and results obtained are presented; mathematical details appear in appendixes. Step 1 considered the equations describing the behavior of reservoir-aquifer systems. The required solutions gave p vs t in a reservoir with constant compressibility being produced at a constant rate and receiving water influx from either a radial or a linear aquifer. Stop 2 modified the solutions to include changes in production rate and reservoir compressibility during the reservoir's history. A computer program was written to predict reservoir behavior using the method derived in Steps 1 and 2. In Step 3 the method's accuracy was verified by comparing results with those obtained with a more exact tank-type simulator. In Step 4 a computer program was written to estimate values for the reservoir parameters that best matched the given history. STEP 1: MATHEMATICAL MODEL This step is concerned with the equations describing behavior of reservoir-aquifer systems. First, a radial aquifer is discussed, and then linear aquifer theory is presented. SPEJ P. 123

Oil and Gas Occurrences in Disturbed Belt of Southern Alberta and Northern Montana: ABSTRACT

Several of the most important hydrocarbon occurrences are briefly summarized in order of discovery and development. The hydrocarbon trap at Turner Valley is primarily structural; however, there are some indications of pre-structural stratigraphic control of accumulation. The Highwood structure, 2 miles west of Turner Valley, has tested only water from the Mississippian. Producing porous zones at Turner Valley can not be easily correlated with porous units at Highwood, indicating that there may never have been a direct connection between the two reservoirs. In addition, some wells drilled east of Turner Valley have encountered tight Turner Valley producing zones. Gas reserves originally in place at Turner Valley were 1.74 trillion cubic feet. Hydrocarbons at Jumpingpound are structurally trapped in the updip edges of a thrust-faulted Rundle slice. Jumpingpound will eventually produce about 700 billion cubic feet of gas. Surface geology in the Pincher Creek area does not suggest the presence of an anticlinal fold or large thrust sheet at depth. In contrast to steep west-dipping surface beds, the Mississippian rocks of the reservoir block at Pincher Creek dip southwest at only 4°-8°. Pincher Creek accumulation is structurally controlled. Current estimates give Pincher Creek 2.29 trillion cubic feet of gas reserves. During the past 5 years, four more important discoveries have been made in the Waterton and Castle River areas near Pincher Creek. Structurally these blocks lie above and west of the Pincher Creek block. Total in place Mississippian gas reserves in Southern Alberta fields currently stand at 8 to 8.5 trillion cubic feet. Early and recent oil and gas occurrences in the Montana part of the are briefly reviewed. Wildcat density, time of structural movement, degree of crustal shortening, and Mississippian stratigraphy are suggested as possible reasons for lack of economic success in the Montana part of the disturbed belt. Mississippian stratigraphy and its influence on hydrocarbon accumulations near the disturbed belt are illustrated with the suggestion that the combination of proper stratigraphic and structural conditions have not yet been found in the Montana disturbed belt. End_of_Article - Last_Page 117------------