Abu Dhabi Oil Co., Ltd. (ADOC) is currently operating three oil fields; Mubarraz, Umm Al-Anbar (AR) and Neewat Al-Ghalan (GA) fields. The oil production of Mubarraz field commenced in 1973, and AR and GA fields initiated oil production in 1989 and 1995 respectively. Since produced water from Mubarraz field has been increasing, water treatment is becoming one of the most important technical elements for stable operations. At the same time, the activities for environmental protection have been intensively promoted, especially, minimizing emissions, effluents and waste discharge. ADOC's operations for water treatment are significantly complex, because it is closely linked to the operations of oil production, gas injection, oil and gas processing, and sewage and desalination. This paper presents several projects and technical improvements in water treatment, and future challenges in ADOC's operations.
Since 1999, Japan Canada Oil Sands Limited has been producing heavy oil derived from oil sands in the Hangingstone field, northeastern Alberta, using Steam Assisted Gravity Drainage (SAGD) technology. In order to follow severe environmental policies in Alberta, water recycling is mandatory to operate SAGD that needs a large amount of steam. Injected steam is returned as produced hot water, which is recycled as boiler feed water (BFW). However, the produced hot water contains dissolved organic compounds (DOCs) that give trouble to water recycling system, such as boiler tube leakage. Under the system where DOCs are supplied from oil sand reservoir, our study result for DOCs showed that it is very difficult to remove DOCs from BFW in a technical and/or economical way. To date, the water recycling system has been improved with a concept that DOCs can not be as concentrated in the BFW line as possible. DOCs are concentrated into disposal water, which is injected to a disposal zone. The actual result that water recycling ratio is now over 90% ranks high.
In Venezuela, Teikoku has been operating oil fields in two blocks since 1992. In the Copa Macoya gas field located East Guarico Block, Teikoku has conducted skin by-pass fracturing (hydraulic fracturing to bypass near-wellbore damage) in 2004 through 2005. Copa Macoya fields consist of lower Oligocene coastal sandstone (5-10ft) at a depth of approximately 7,000ft subsea level. According to well tests, permeability range in this reservoir from 100 to 1,000md, however skin factors show around 50 in several wells. It was considered that the reasons of high skin factors resulted from severe damages during drilling operations and/or workover operations. In order to remove these, the skin by-pass fracturing was done in two wells. These fracturing operations were successfully completed and resulted in a decrease of the skin factors to almost zero after main treatments. The design points and the results of skin by-pass fracturing operations in the high permeability reservoir are presented in this paper.
Techniques of sand control are roughly divided into three types. One is control of production rate, next is using screens such as gravel pack, and the last technique is screen-less method. Japan Petroleum Exploration executed the screen-less sand control to the new well of the Amarume oilfield in Yamagata Prefecture in 2003, and Japan Petroleum Exploration and Mitsubishi Gas Chemical executed the through-tubing gravel pack (TTGP) to the existed well of the Higashi-Niigata oil & gas field in Niigata Prefecture in 2004. Both operations were the first trials in Japan and are presented about the outline of the work in this paper.
Vertical sweep efficiency in heterogeneous carbonate reservoirs is one of the largest uncertainties of the reservoir management for five-spot-pattern water flooding in Abu Dhabi. Intensive water cut monitoring at the producing wells is the key element to optimize reservoir management by water flooding operation in this field. Installation of multiphase flow meters (MPFMs) may enable to provide the operators with continuous and real-time water cut data. Then the two sets of the JOGMEC/OVAL MPFM were installed and commissioned in a giant oil field in Abu Dhabi, and the monitoring of well streams was conducted from August 2002 to December 2004. The MPFM incorporates a new turbine system consisting of twin-rotors with conventional technologies, while eliminating expensive gamma ray densitometry and minimizing the size, thus successfully achieving great cost reduction and easy installation. The MPFMs custom-made for the liquid production range of 5,300-8,100 BLPD continuously measured oil and gas rates within +/-10% relative error and water cut within +/-3% error. The high accuracy of the MPFM monitoring liquid and gas rate was confirmed by the referential test separator data. However further confirmation is required for water cut monitoring by MPFMs, because enough referential sampling data were not available for comparison of water cut. On the other hand, it was confirmed that the accuracy of the reference data directly affects the water cut. Therefore, more samples of accurate reference data are indispensable for good result of MPFM monitoring and also the MPFM needs to take measures for reducing the error of the water cut. It was learned from the experience of this field trial that the most important point for the improvement of any MPFM is for MPFM vendors and operators to confirm the ability of MPFMs with using “the accurate reference data” in the same fields. It will enable operators to confirm the true ability of MPFMs in the fields and use MPFMs as a reliable reservoir-monitoring tool for better reservoir management.
In the South Kanto natural gas fields, Japan, natural gas which is dissolved in water is produced mainly by gas lift through a perforated casing. Since the number of new production wells developed each year is restricted due to regulations relating to environmental preservation, a technique for improving poorly performing wells by perforating a casing is necessary to increase natural gas production. Furthermore, a casing pipe must be perforated for cementing when a well is abandoned to prevent natural gas from leaking along the pipe. In this study, we proposed a new system with abrasive waterjets for perforating steel tubing without using shaped explosive charges or coiled tubing. Since slurry pumps are not economical for supplying abrasives from the surface to great depth, we adopted a batch type system with a tank for supplying abrasives. To clarify the effect of ambient and driving pressures on both the mass of abrasives and the impinging time that are required for perforation, laboratory perforation tests were conducted under high ambient pressure. Main results obtained in this study are summarized as follows: (1) The developed system can perforate steel tubing with a thickness of 4.15 mm under a high ambient pressure of up to 7 MPa. (2) Both abrasive mass flow rate and the mass of abrasives required for perforation increase with ambient pressure. However, the increase rate with respect to the ambient pressure of the former decreases while that of the latter increases with ambient pressure. As a result, the impinging time required for perforation is minimum at a certain ambient pressure. (3) The mass of abrasives required for perforation and the impinging time required for perforation are governed mainly by two factors; cavitation number and the difference between driving and ambient pressures.