PEMEX and TRC/JNOC commenced the collaborative research project “Geo-statistical modeling of Chicontepec reservoirs: Agua Fria, Coapechaca and Tajin areas” in 1999 for the purpose of the technology development to integrate geological, seismic and reservoir engine-ering information for better field development and reservoir management. This paper presents the procedure of pixel-based hierarchical geostatistical modeling of sandstone distributions in turbidite deposits of the Agua Fria, Coapechaca and Tajin areas in the Chicontepec basin. The Paleogene Chicontepec Basin is located between the Sierra Madre Oriental and the Golden Lane Platform, extending northwest to southeast along the Gulf Coast in Mexico. This basin consists of submarine fan turbidite sandstones derived from the Sierra Madre Oriental. First, geological/sedimentological analyses were conducted based on the concept of sequence stratigraphy for the purpose of stratigraphic division and facies distribution estimation. Four turbidite facies were recognized based on well-log patterns and core descriptions. These estimated facies distribution maps are compared with the results of seismic facies analyses. Second, an architectural framework for each sequence boundary (SB) and sub-internal surfaces of trangressive surface (TS) and minor condensed section (MCS) was modeled by integration of sequence-stratigraphic well-marker data and depth-converted seismic time horizons. The non-parametric Alternating Conditional Expectation (ACE) algorithm was used to develop correlation functions between nine kinds of seismic attribute data and total porosity (PHIT). Finally, three-dimensional distributions of PHIT, shale volume contents (Vsh) and facies distribution were modeled using various geostatistical techniques. A special technique is presented for the integration of seismic and well data, which also simultaneously honors sub-interval-layering information. Comparison of geostatistical facies model with deterministic geological models shows general agreement between the two. However, the integrated geostatistical method generates much more detailed information and is readily applicable to wider reservoir areas.
Teikoku Oil Co., Ltd. operates Minami-Nagaoka gas field, one of the biggest natural gas fields in Japan. Increasing demand of natural gas requires that Teikoku Oil should reinforce its production capability, including number of production wells, in Minami-Nagaoka. From a viewpoint of stable supply of gas resources, importance of natural gas underground storage has been widely recognized. Teikoku Oil established, for the first time in Japan in 1969, the underground storage system in Sekihara gas field, which was a depleted gas reservoir located a few kilometers north to Minami-Nagaoka. Since then, it has played a great role for peak shaving and/or emergency stockpile in Minami-Nagaoka gas production operation. At present, approximately 140 MMNm3 of natural gas is stored with the maximum deliverability of 1.6 MMNm3/day. Some technical issues encountered and solved during the storage operation for these 30 years are discussed in this lecture. In addition, Teikoku Oil notices that its experiences gained through the underground storage of natural gas in Sekihara could be directly applied to underground storage of carbon dioxide. Namely, injecting and storing man-made emissions of carbon dioxide, a greenhouse gas, in underground is considered as one of the possible measures against a global warming problem. Teikoku Oil is a member of a national research project on the underground storage of carbon dioxide led by RITE (Research Institute of Innovated Technology of Earth) and SEC (Safety and Environment Center for Petroleum Development). A pilot test to inject and store 15, 000 tons of carbon dioxide into a water zone is scheduled in and after 2003, for which one injection and two observation wells have already been drilled in Minami-Nagaoka. This noteworthy project is also introduced in this lecture. A key concept common to the both topics above is “utilization of depleted gas/oil reservoirs.”
Abu Dhabi Oil Co., Ltd. (Japan) operates three offshore oil fields, namely Mubarraz, Umm Al-Anbar (hereafter referred to as AR) and Neewat Al-Ghalan (hereafter referred to as GA) Fields, in Abu Dhabi, United Arab Emirates. AR and GA Fields are oil fields containing high concentration of H2S and CO2 within the associated gas, which are highly corrosive to metal and extremely toxic to humans. The highest levels of precaution for safety were taken in the development policy as well as in the design of the facilities. Meanwhile, gas injection into oil reservoirs had been planned for EOR from the commencement of production, which in turn met the gas conservation policy of Abu Dhabi Government. Given that high-pressure sour gas injection technology was not available in the mid-1980's, H2S and CO2 in produced sour gas had to be extracted by a gas sweetening unit and the sweet gas was then injected into the reservoirs. The sour gas fed from low-pressure separators and acid gas fed from the gas sweetening unit were flared at the artificial island located at the center of the AR Field, namely AR Site Terminal. Since then, various methods to resolve this flaring issue, such as sulfur recovery, production of fertilizer or plaster and disposal of liquid sulfur into underground formations, etc. have been investigated and studied as a priority. However, none of them were economically and/or technically feasible. After a site survey in Calgary, Canada, and in-house extensive studies, it was concluded that sour gas injection was technically and economically feasible. The basic engineering study was commenced in November 1997, and the detail engineering was started in March 1998. The facilities for the sour gas injection were constructed between July 1999 and May 2000 in AR Site Terminal, comprising of two units of low and high-pressure sour gas compressors and one sour gas dehydrator. At the initial stage of the commissioning of the facilities, problems such as vibration of the low-pressure compressors and scale plugging at the strainer were encountered, which caused the delay in the completion of the project. After resolving these difficulties in November 2000, the sour gas injection has been working successfully. The sour gas injection is the first challenge in the Arabian Gulf region, achieving gas conservation, environmental protection and enhanced oil recovery, simultaneously.
An isothermal, oil-water, two phase system for thermal recovery methods was studied experimentally to understand the influence of temperature on their fluid-rock properties such as irreducible water saturation, residual oil saturation, relative permeability and mobility ratio. And the temperature dependency of these parameters was quantitatively discussed. It was found that these parameters were all shifted to work to increase the fluid-rock properties of oil, hence to increase the oil recovery. A computer simulation model of isothermal, two phase-system for thermal recovery by hot water flood was developed, incorporating the temperature dependency of these parameters experimentally defined in this study. It was found that for a relatively light oil, improvement of relative permeability was the most effective mechanism to improve oil recovery by increasing the formation temperature, though decrease of oil viscosity was most effective for heavy oils.
The vitrinite reflectance (Ro) and statistical Thermal Alteration Index (stTAI) of the 12 samples from MITT Sanriku-Oki borehole drilled in the Pacific Ocean off the east coast of Honshu Island were measured to investigate organic maturation and the effect of unconformity on organic maturation in this borehole. This borehole is composed of sediments from the late Cretaceous to Quaternary and has two unconformities at 1, 683 and 3, 535m in depth from sea level. The vitrinite reflectance shows a general tendency to increase with increasing depth having some dispersion, and is not influenced by the unconformities. Although the statistical Thermal Alteration Index regularly decreases with increasing depth, it made a large difference between in the upper and in the lower zones than the unconformity at 3, 535m. This unconformity means that sedimentation was interrupted for about 9 million years between early Maastrichtian and early Late Paleocene. It is suggested that Ro is a maturation parameter more sensitive to temperature than to heating time, but oppositely stTAI is a parameter more sensitive to heating time than to temperature. It is shown with both data of Ro and stTAI that organic maturation reaches the stage of petroleum generation, 0.5% in Ro and 110-145 in stTAI, at 3, 400m in depth.
Soupy disturbances appeared in the long piston cores taken from the Oki Ridge, off Shiretoko, off Kashima and off Kochi during IMAGES Vil-WEPAMA Leg 2 (May-June 2001). The soupy disturbance layers were cold when the core was recovered, and they expelled the mixture of gas, water and mud through drilled holes of the core liner tube. This suggests the dissociation of gas hydrates in the core onboard. Because the presence of soupy disturbance does not prove the existence of gas hydrate by itself, we need to obtain additional evidences in a future long piston coring study.
There are many exposures of Neogene subaqueous volcanic rocks on the Kakuda to Yahiko beach through Maze beach, Niigata Prefecture, Japan. In this paper, I am giving several criteria for recognition of the subaqueous volcanic rocks by showing the examples exposed on these beaches. The Kakuda beach is characterized by andesitic hyaloclastites associated with lava lobes fed from feeder-dykes. The andesitic hyaloclastites are classified into pillow fragment breccias and angular fragment breccias. The Maze beach is diagnostic of basaltic lava fountain deposits interbedded with remarkable pillow lobe layers. The basaltic lava fountain deposits include water-chilled spatters/bombs and in places pillow lobe fragments, all of which were thrown into water, followed by fall-back repeatedly, onto a slope, to form a turbulent flow deposit. The pillow lobes have in places multiple-crusts and pipe-vesicles in cross section, and spreading cracks on the surfaces. Volcanic rocks of the Yohiko beach is characterized by rhyolitic lavas associated with perlitic hyaloclastites. The rhyolitic lavas show typical ramp structures, and the perlitic hyaloclastites have in particular been subjected to completely clay.