Core holder

Procedure. Core floods were carried out in horizontally mounted Berea sandstone cores of length 61 cm and diameter 5 cm. Porosity varied from 18 to 25% and brine permeability from 100 to 800 Jim2. The cores were coated with a thin layer of epoxy and cast in stainless steel core holders using molten Cerrobend alloy (melting point 70°C). The ends of the cores were machined flush with the core holder and flanges were bolted on. Pore volume was determined by vacuum followed by imbibition of brine. Absolute permeability and porosity were determined. The cores were initially saturated with brine (2% NaCl). An oil flood was then started at a rate of lOm/day until an irreducible water saturation (26-38%) was established. 

The core is put into a Hassler sleeve inside a core holder where overburden pressure is applied outside of the sleeve by using water. Gas is not used, since it has the potential to diffuse through the rubber sleeve. The overburdened core holder is connected to the Isco pump, from which 1% acidified brine is pumped into the core. The needle valve that restricts flow from the output end of the core is opened slightly to allow the escape of air and air-saturated brine. The needle valve which restricts flow from the input end of the core is opened fully. Complete saturation is attained after several pore volumes of brine have been pumped through the core under pressure, and this fully saturated core is used throughout the experiment. 

Fig. 8. Design of angular circular extrusion head with rotating core for manufacturing of tubes and hoses 1 — Single-screw extruder 2 — Adapter 3 — Core holder 4 — Separable core tip 5 — Alignment bolts 6 — Rotating core 7 — Plain bearing 8 — Stop flanging 9 — Head casing 10 — Electric heaters 11 — Place for installation of thermocouples...

Because these core were not permeable to water even at high pressure, they were mechanically split to provide a path for water flow. To split the core, a sharp, hardened steel edge was pressed along the length of the core, using a hydraulic press, until the cores fractured. Details of the operation and the mounting of basalt cores in the core holder vessel can be found elsewhere (3). 

Berea sandstone cores (25.4 cm by 3.8 cm) used in the experiments with Wilmington and Delaware-Childers crude oils were fired at 427°C. After firing, the cores were saturated with brine, mounted in a Hassler type core holder, and placed in a temperature-controlled oven. After initial absolute permeability was determined, the cores were left either oil-free or saturated with oil and waterflooded to residual oil saturation. 

The core experiments with Kern River oil were performed using sandpacks (25.4 cm by 3.7 cm) made from unconsolidated field core. The core material was packed into Teflon sleeves with Teflon end caps and then placed into a Hassler type core holder. Before packing, the sand was cleaned by Soxhlet extraction with toluene and was not fired. Otherwise, the procedure was similar to that for saturating the consolidated Berea sandstone cores. 

An example of a joint density function gA (r, R) is shown in Fig. 12. The sample is a Bentheimer sandstone in a rectangular parallelepiped shape 50 mm long extending in the -direction, 25 mm wide along the x-direction, and 5 mm thick in the y-direction. The average volumetric flow rate of the water was 1.5 ml min-1 along the -direction. The sample is located between the two spikes resulting from free water present in the end caps of the core holder. 

Recombined oil (also referred to as live oil ) was prepared by saturating the oil with methane gas in recombination equipment connected to the inlet end of the core holder. Produced fluids were collected into a graduated cylinder placed on an electronic balance for measuring the oil production rate. An automated data acquisition system was employed for recording of the oil-production rate and the differential pressures in each segment during the flow experiment... 

Figure 6 shows how the critical salt concentration is determined. A core sample is saturated with a suitable salt solution and mounted in a standard core holder and coreflood apparatus. Salt solution is then injected at a specified superficial velocity. Subsequently the salt concentration is reduced in small steps until a decrease in permeability is observed (36). 

Water is circulated through the specimen, confined within a Viton sleeve, and pressurized by the confining fluid within the core holder. Flow rates are prescribed. 

Figure /. Schematic of flow-through experiment for the novacutite experiment. Scan section, lines and numbers are relative to core holder base (in mm).

With the arrival of perforated bricks, dies had to be provided with suitable cores, core holders and core holder bows. Tests were made with so-called bow-less dies with the cores fixed to wires, but these proved to be unsuccessful. With the design of dies becoming more and more complicated, die-making developed into a special field within ceramic machinery engineering, and even today there are still a few companies in various countries who manufacture exclusively dies. 

The porous medium consists of unconsolidated Ottawa sand contained in a cylindrical lucite or lexan polycarbonate core holder. 

A plastic core holder is used to minimize attrition during dry packing of the sand, to eliminate secondary loss of chemicals at the wall (e.g., reaction to form rust) and to allow flow visualization of the saturation fronts. The Ottawa sand is sieved and thoroughly cleaned in order to obtain reproducible surface characteris-... 

Geffen et al. (6) Caudle et al. (7) Richardson et al. (8) Schneider and Owens (9,10) McCaffery (11)). The schematic diagram of the relative permeability equipment is shown in Figure 1. In the present study the two fluids injected simultaneously at a fixed ratio of flow rates were Soltrol 160-oil (1.5 cp viscosity) and 2% NaCl brine. The cores were mounted horizontally in a modified Hassler-sleeve core holder as shown in Figures 2a and 2b. All experiments were run at room temperature. All of the materials used in the flow system were inert to the test fluids (1). The Ruska constant rate proportionating pumps, used by most of the earlier investigators to displace the two liquids were replaced, for reasons of economy, with hydraulic actuators driven mechanically by D.C. electric motors via variable transmission controls (1). 

Fig. 2a. Cross-sectional drawing of modified Hassler-sleeve core holder used for Berea 11, Berea 12, and Berea 13 samples,...

The sample to be treated with Dri-Film SC-87 solution in hexane was loaded into the Hassler-sleeve core holder and about 60 pore volumes of Dri-Film solution was passed through it in both directions and, subsequently, it was flushed with about 25 pore volumes of N2 gas. On removal from the core holder the sample was dried at 225°F for about four hours and after cooling it was weighed. 

The fluid flows through the switching valve (V) and enters the core holder (shown in Figure 2), The core holder is placed in a constant temperature bath. The valve (V) is a six port, high pressure micro-volume valve which allows the fluid being pumped to the core to be switched quickly and sharply. Once the fluid leaves the core holder, it is either collected for analysis or discarded. 

A detailed diagram of the core holder is shown in Figure 3. 

Fig. 3. Sandstone core holder 1) sandstone core 2) tygon rubber sleeve 3) top core end plug and electrodes 4) bottom core end plate, end plug, and electrodes 5) top core holder end plate 6) pressure inlet for N2 overburden pressure 7) outlet stem 8) water inlet.

The saturated core is placed in the core holder and its initial permeability (K ) of the sandstone core is then measured by pumping a 30,000 ppm of sodium chloride solution at a constant... 

During the enhanced recovery using the core rock, 0.45 g of oil was collected and the produced water phase was still cloudy with the presence of the surfactant. For the oil specific gravity of 0.83, 1 pore volume corresponds to 8.3 0.8 g of oil. For a total recovery of 10.45 g of oil, this means that the surfactant was able to recover the last remaining oil in the core holder additional volume of recovered oil came from the fiow lines which amounted to 2 ml (1.9 g) at most. Also, from this example run, the multifunctional multipolymeric surfactant was capable of delivering about three times the amount of oil compared to that of tertiary recovery waterflooding. 

Two core plugs from a carbonate reservoir (calcite) were used [68]. One core holder held a high permeability core (initial brine permeability = 535 mD) and the second core holder had a low permeability core (initial brine permeability = 3.1 mD). The cores and floating-piston eeUs were placed inside a temperature-controlled oven. Foam quality was varied by adjusting the flow rates of nitrogen and the snrfactant solution while keeping the total flow rate at 5 cm /min. 

At first, core was measured with a vernier caliper to get its diameter and length, then it was vacuumpumping and saturated by formation water. After that, the core was put into the core holder to plus confining pressure 2.0 MPa. When the process was turned on, core was injected displacement of formation water forward, core was flowed the displaeement fluid more than 10 times the pore volume until the flow was stable. The core permeability K was calculated, then 2 PV the gel... 

Cores cut from outcrops that are quarried for building stone are commonly used in studies of oil recovery. For this study a total of 61 core plugs, each with a nominal length of 0.5 in and a nominal diameter of 1.5 in, were cut from 19 different rocks. Some of them are cunently in use for laboratory studies of oil recovery. 18 of the core plugs were carbonates (lim tones) and 43 were sandstones. The cores were washed, dried at ambient temperature for one day and then oven dried at 110 C for two days. The permeability to nitrogen, kg, was measured in a Hassler-type core holder at a confining pressure of 2.07 MPa (300 psi). Porosity was calculated from the increase in mass after saturation under vacuum with water. Permeability, porosity, BET surface area and cation exchange capacity (CEC) of each rock sample are listed in Table 1. 

The polymer rheology in porous media is often measured by coreflooding experiments. Figure 1 shows a typical coreflooding apparatus. It is mainly composed of a pump used for pumping distilled water, piston accumulator used for polymer storage, core holder or sandpack, and pressure gauge or transducer to record injection pressure. 

The linear displacement apparatus shown in Fig. 1 consisted of the injection and sample gathering system, the core holder, and the pressure sensing system. An ISCO Model 312 metering pump was used to inject fluids into the core at a constant flow rate. Effluent stream samples were collected in 9-ml test tubes with a Gilson Model FC-80 Micro Fractionator. 

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