An automated and compact multiphase flow meter (MPFM) tested offshore Saudi Arabia has accurately measured three-phase flow rates under existing field operating flow conditions. A three-month field test was conducted utilizing over 160 well tests under varying operating conditions. A meter was installed on an offshore test barge, so that individual wells could be tested in series with traditional test separator methods. For these trial tests, the total liquid rate ranged from about 335 to 12, 333 barrels per day, the GOR ranged from about 67–185 SCF/STB and the water cut ranged from 0 to 70%. The results show that over 93% of the well tests were within +/- 10% of test barge results for all liquid, oil and water cut measurements. While gas measurements were determined to be within +/- 15% in 63% of the wells tests. Also, the results for the gas measurement comparison are discussed although the gas measurements were evaluated against historical field PVT data, due to the unavailability of a valid test barge gas rate comparison meter. The project platforms currently identified for multiphase metering differ in physical size and vary from single well to 8 well configurations. For accurate reservoir management, each well is individually rate tested to monitor well performance and to provide data for field allocation and planning purposes. The wells are presently being evaluated by test barges, which are equipped with testing facilities. A multi-phase flow meter was successfully field-tested as an alternative to the use of the test barges. Permanent multiphase flow meter installations will provide more frequent tests and considerable economical savings in the long run. Introduction The Safaniya Field, which is the largest offshore oil field in the world, has 146 existing offshore platforms. These platforms differ in physical size and vary from single well to 8 well configurations. For accurate reservoir management, each well is individually rate tested to monitor well performance and to provide data for field allocation and planning purposes. The wells are presently being tested by two barges, which are equipped with testing facilities. These barges are approaching obsolescence and require extensive maintenance to maintain the current testing schedule. In addition, numerous offshore platforms are located in areas that are inaccessible to the barges and cannot be easily tested. The barges are also prevented from testing wells approximately one third (1/3) of the time each year due to adverse weather conditions. Furthermore, well testing requirements for the Safaniya field are increasing dramatically due to higher water cuts as the field matures, more wells being drilled, and fluctuations in the field production requirements. It is projected that by 2007, the field will require at least three new test barges to maintain the current testing standards. As a result of the inefficiency and limitations of the test barges, a couple of multiphase meters have been successfully field tested as an option instead of ongoing use of the test barges. Multiphase flow meters will provide the Safaniya field with more frequent tests and considerable economical savings in the long run. Meter Description The PhaseWatcher multiphase meter trial tested in Safaniya field is the latest multiphase flow meter being offered by Schlumberger. This meter measures oil, gas and water rates without separation of the production stream, and calculates flow rates for actual and standard conditions. The portable meter is a compact unit [1.5 meters × 1.6 meters × 1.7 meters] consisting of a typical venturi section with upward vertical flow. In addition, a dual energy gamma ray meter is utilized at the throat of the venturi for measuring oil, water, and gas fractions. Dual Energy Gamma Fraction Meter Calculations of oil, water and gas fractions are based on the attenuation of two different gamma energy levels of a radioactive isotope. The gamma ray contains different energy levels, and the attenuation of two of these energy levels can, by physical equations be expressed as a function of oil, water and gas volume fraction.
Saudi Aramco has embarked on developing an oil field located in the Northern area of Saudi Arabia. This field is characterized by the presence of tar-mat zones that are present at the base of oil-column. These zones form a barrier which physically isolates the producing zones and the injection water. This paper addresses the challenges faced in maintaining the injectivity of water in this particular field. Open-hole water injectors with extended reach (ER) were completed horizontally at the bottom of the producing zones and just-above the tar-mat zones. The typical open-hole lengths in these wells are between 3,000 -7,000 ft. Challenges were faced in drilling these wells in a populated area in the northern area of Saudi Arabia and being stratified, tar-mat was encountered in the open-hole sections of these wells. Tar content varies inconsistently around these injectors. This limits the injection rate of these injectors initially to as low as 600 BWD at 2,400 psig. The low-injectivity of these water injectors is attributed to the damage induced by the drilling mud (water-based mud) and the presence of tar and asphaltenes in the injection zone. Acid stimulation treatments of these wells were needed to reach the target injection rates. Furthermore, this particular northern field in Saudi Arabia is sour and located inside a highly populated area and as such, environmental regulations prohibit any well flow back post acid treatment and no flaring is allowed. To overcome these challenges a tailored acid treatment was designed. It included a preflush of an aromatic solvent, then stages of 20 wt% HCl regular and emulsified acids. To achieve better acid diversion in horizontal wells, stages of a surfactant-based acid system were utilized. Along with tailored acid treatments, new methods to place the acid in the zone of interest were also employed. More than 20 extended reach horizontal injectors were successfully stimulated in a sour carbonate oil reservoir. Pre and post treatment injectivity tests were performed using down-hole gauges in order to evaluate the efficiency of the acid treatments. This paper will discuss challenges faced during stimulation of water injectors in this sour heterogeneous reservoir, fluid selection, design criteria, field treatments, lessons learned, and results of the acid treatments. Introduction The development of the northern oil field by Saudi Aramco necessitates 30% of the newly drilled wells to be water injection or water disposal wells. The water injectors are completed with 6 1/8-inch open hole horizontal wells with 3,000 to 7,000 ft open hole section for maximum reservoir contact (MRC) purpose. Most of these wells are considered as extended reach wells.1 Tar zones are present in Field Q, which produces oil mainly from three carbonate reservoirs: AC, AD, and LF.2 The three carbonate reservoirs have different properties. Table 1 provides the average permeability, porosity and grain density of the three reservoirs in Field Q. Reservoir AC has the highest permeability, whereas reservoir LF has the lowest permeability. The grain density of reservoir AD was the highest, indicating higher dolomite content in this reservoir. Peripheral water injection has been used to maintain reservoir pressure and oil production. Tar zones with almost zero permeability act as a barrier that hinders water flow in the reservoir, and as a result, the pressure in some areas will decrease with time. Injectivity tests performed after completion of these injectors showed very poor injection rates, which were attributed mainly to the damage induced by the drilling mud (water-based mud) and the presence of tar in the injection zone. Acid stimulation treatment campaign was launched in 2005 targeting some of the water injectors to increase the injection rate and maintain the required reservoir pressure by peripheral water injection. The following challenges had to be overcome to effectively stimulate these injector wells:Long open hole length ranging from 3,000 to 7,000 ftSignificant changes in the reservoir permeability, which varies from 50 to 1,000 mDSour environment (16 mol% H2S)High tar contentRestriction on well flow back before and after the acid treatments These challenges were addressed by carefully designing acid treatments. The objectives of the present study are to:Discuss factors that affect the design and execution of acid treatments, andAssess acid treatments based on field data.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn April 2002, the first retrievable straddle pack-off gas-lift assembly was installed in a Safaniya onshore well, which had been dead due to high water cut since 1993. This gas lift assembly has successfully increased the well production to an average daily liquid production rate of 2600 barrels with 30% water cut. The significant incremental production of 1800 BOPD is regularly contributing to company profit. This paper discusses in detail the new gas lift equipment, principles of operation, installation, and trial test results. The assembly can be installed and retrieved with wireline, eliminating the need for a workover rig. It is equipped with gas lift mandrels to convert them to gas lift without pulling out the tubing. Based on its simplicity, successful operation, and considerable economical impact, there is a vast potential for this technology in Saudi Aramco.
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