This paper studies the response of fractured reservoirs to the pressure pulses. A numerical model is presented, which is applicable to simulate pressure behaviors of fractured media in three dimensions. This model consists of dual-porosity and dual-permeability in cell. The simulation of the pressure in the fractured reservoirs is formulated in a pair of differential equations treating fluid flow between rock frame and fracture. The paper discribes dynamic behaviors of pressure pulses and discusses fundamental problems associated with injection rate and pulse duration. Also discussed are the effects of reservoir propeties which respond to the applied pressure pulses. It is concluded the dynamic behaviors of pressure pulses in fractured reservoirs give useful information on reservoir properties.
We conducted a drilling test in a geothermal well located in Yamagata prefecture, using a new PDC core bit of 8-15/32in. outside diameter and 4in. inside diameter. The bit has fifty-seven new PDC cutters brazed on a bit body at both backrake and siderake angles of -10 degrees. The bit is characterized by the new PDC cutter used for it. The feature s of the new cutter are as follows: (1) The new PDC cutter has the same materials of a conventional one which has been developed by a maker in Japan for the drilling of hot and hard rock formations. (2) A conventional PDC cutter, whose diamond layer is exposed, occurs chipping of a diamond layer readily in hard rock drilling. Therefore, the diamond layer of the new cutter was almost coated with a tungsten carbide layer to prevent the chipping. The drilling test was carried out at the depth of about 1, 900m in the well. Rock drilled was granodiorite (about 1, 100kgf/cm2 uniaxial compressive strength) and rock temperature reached to around 250°C. Bentonite mud was used as a drilling fluid. The bit weight was changed between 0.6 and 12ft to obtain a constant penetration rate of about 2cm/min. The mud flow rate and the rotary speed were kept constant at 1m3/min and 27rpm, respectively. Drilled length of the bit reached to about 5m. The degree of wear or chipping of the PDC cutters after drilling was estimated approximately 60%. From the results of the drilling test, it became clear that the new PDC core bit can be applied to the drilling of heterogeneous, hot and hard rock formations.
This paper is an excursion report to get the information of steam injection operations to recover the heavy oil from deep formations in Riaohe oil field. Riaohe oil field is located in the sourthern district of north-eastern China, surrounded by the area from west side of Shenyang to Bohei along the Riaohe river. The central office of this oil firld is very convenient to be able to arrive within 4 hour drive through the high way from Luda. We discussed the steam injection and recovery processing tecnology with chinese researchers of the oil field during the excursion. In this paper, general geology of Riaohe oil field was descrived. Heavy oil recovery operations of two oil fields, Gaosheng and Shugang, were introduced, specially on reservoir and fluid properties, steam injection well completion, injection water preparation, control of generated steam quality and production facilities etc..
A CO2 tertiary flood is being studied in Kubiki field, which located in Niigata prefecture facing the Japan sea, since 1988 with an inverted four-spot pattern. First 3 year of the project was spent for pre-injection study. Well logs and core analyses were used to predict the residual oil saturation. Bottom-hole fluid sample was taken to measure PVT properties including MMP and to perform core-flooding under reservoir condition. Using these results, numerical simulation both for water-flooding stage since 1977 amd CO2 injection stage is now being preformed. The present paper summarizes the result of these pre-injection study. CO2 injection was commenced on February, 1991. The design rate of the injection plant is 15 tons of CO2 a day. During injection, well logs and fluid samples are taken periodically and bottom-hole pressures are automatically recorded to a personal computer by the surface readout bottom-hole pressure monitoring system.