The reservoir has been in production since 1954 but new wells continue to find pockets of porosity at initial reservoir pressure. Porescale network modeling of microporosity in low resistivity pay zones of carbonate reservoir article pdf available in journal of natural gas science and engineering 71. Presence of micrite, in carbonate system is the main cause for low resistivity in reservoirs of d1 field. Paper open access related content elastic and electrical. By low resistivity pay sand, one infers that the reservoir contains a commercial quantity of hydrocarbon but the resistivity log reads low, in other words, resistivity log is unable to adequately see. Reservoir characterization and pore type systems of. Carbonate reservoir characterization and estimation of fluid saturation seem more challenging in the low resistivity pay zone lrpz. The determination of accurate hydrocarbon saturation is more tasking due to their complex and heterogeneous pore structures, and. The pay zo ne includes carbonate reservoirs that resistivity logs have a resistivity between 6 to 1 ohmme ters and even in some intervals reach less. A practical approach to determine lowresistivity pay in. Although thin, some low porosity layers act as traps within the overall reservoir, just as they do in the arab d and other carbonates in the middle east. Clean oil bearing sandstone has high resistivity, but when this rock contains shale, or heavy minerals such as pyrite, the resistivity can become low.
The lower cretaceous buwaib formation is important reservoir in the persian gulf. Resistivity resistivity of saline water rw resistivity of water and formation resistivity of water, hydrocarbons, and formation resistivity of tight formation no porosity increasing resistivity resistivity tool background three classes electrode logs laterologs focused electrodes induction measure resistivity in ohms. Well log analysis for reservoir characterization aapg wiki. Pdf a cohesive approach at estimating water saturation. Porescale network modeling of microporosity in low. In practice, conductivity units are typically used when referring to water ranging from drinking water to sea water, while resistivity units are reserved for ultra pure water such as deionized or reverseosmosis water. This is the only commercial course that addresses this critical parameter in. Recognition and evaluation of lowresistivity pay paul f. Spe177709ms evaluation of water saturation in a low resistivity pay carbonate reservoir onshore abu dhabi. Psrhythmic carbonate versus spiculite deposition in mississippian hydrocarbon reservoirs in the midcontinent usa. Petrophysical characterization of carbonate naturally. An integrated approach conference paper pdf available november 2015 with 938 reads. The user will be able to interpret the lithology by using several logs, there are gamma ray, spontaneous potential, resistivity, and density log. Reservoir characterization of carbonate in low resistivity pays zones in the buwaib formation, persian gulf.
Pdf reservoir characterization of carbonate in low. According to schlumberger market analysis 2007 sheng, 20, carbonate reservoirs hold 60% of oil and 40% of gas reserves in the world. A cohesive approach at estimating water saturation in a. Pdf porescale network modeling of microporosity in low. Spe177709ms evaluation of water saturation in a lowresistivity pay carbonate reservoir onshore abu dhabi. Reservoir characterization of carbonate in low resistivity. Resistivity in core saturated completely with salt water was measured to different overload pressures. Carbonate reservoir characterization and fluid quantification seem more challenging than those of sandstone reservoirs. The concept of causes for lowresistivity and lowresistivity contrast pay have been enriched over the years. Interpreted reservoir saturation data from the rstpro reservoir saturation tool using geoframe reservoir characterization software to enable more accurate and timely decisions. Low contrast pay low resistivity pay and low contrast pay have been recognized.
Accurately and representatively measure oil saturation in lowresistivity carbonate pay, an environment where the traditional archie equation overestimates water saturation. Lowresistivity pay in a complex chert reservoir scott l. However, many productive reservoirs have low apparent resistivity values, and remapping these intervals using modern petrophysical techniques can have significant production and reserve implications, especially in mature fields. Low resistivity oilgasbearing reservoir conductive model. Understanding low resistivity heterogeneous carbonate pays. Highresistivity soils are generally not as corrosive as lowresistivity soils. Conductivity is simply the reciprocal of resistivity. These reservoir zones show low resistivity characteristics, high fluid. Based on the characteristics of low resistivity reservoir indicated by well logging plot, the genesis of low resistivity reservoir is systematically studied in aspects of petrophysical property, reservoir height, cationexchange in shaly sand, invasion of filtrate in drilling and. This response of low resistivitylow contrast is due to the low vertical resolution of the conventional logging tools, which can not measure thinbedded pay zones. Lowresistivity pay lrp has been a challenging problem in formation evaluation for many years. From model to implementation conference paper pdf available november 2016 with 482 reads. Earthstar ultradeep resistivity service was able to geomap the complex carbonate reservoir and multiple resistivity layers.
Therefore, its not surprising that the research on carbonates has been and continues growing. Shaly sands reservoir is one of the most distributive types of the oilgasbearing reservoirs discovered in china, and low resistivity oilgasbearing reservoirs are mostly shaly sands reservoirs. Understanding low conductivityhigh resistivity measurements. A cohesive approach at estimating water saturation in a lowresistivity pay carbonate reservoir and its validation adedapo awolayo1 ayham ashqar2 miho uchida2 andi ahmad salahuddin2 saheed olawale olayiwola2 received. The li reservoir of mumbai high is the shallowest limestone reservoir which produces oil, and has low resistivity character. The reservoir characterization of low resistivity pay has been challenging due to high reservoir heterogeneity1. Therefore, shaly sands reservoir conductive model is the key to evaluate low resistivity oilgasbearing reservoirs using logging information. Although lrp can occur in both sandstone and carbonate reservoirs, it is more common in sandstones. Successfully drilled each hole section in a single run, with the downhole drilling and logging. Developed approach for better understanding of low. In the middle east region, however, they account for 70% of oil and 90% of gas reserves sheng, 20. The reservoir characterization of low resistivity pay has been challenging due to high reservoir heterogeneity 1.
Presence of secondary porosity is also adding the heterogeneity in reservoirs of this field. Lowresistivity pay is a longstanding problem in formation evaluation. A cohesive approach at estimating water saturation in a lowresistivity pay carbonate reservoir and its validation a awolayo, a ashqar, m uchida, aa salahuddin, so olayiwola journal of petroleum exploration and production technology 7 3, 637657, 2017. In carbonate, reservoir heterogeneity is the key player in the flow performance, and in socalled low resistivity pay reservoirs, the rock contains pores of a significant varying pore sizes, most of these pores are micropores resulted from large abundance in peloids and micritized organisms figure 1 and has a bimodal or even trimodal. Several numbers of technical papers described on the possibility of finding the low resistivity pays. Before analyzing the field examples, the basic principles of nmr and their effect on the interpretation are discussed. To overcome this challenge when drilling in a lowresistivity carbonate reservoir in libya, an. Carbonate reservoirs characterization and fluid quantification looks more challenging than sandstone reservoirs. Causative factors and resulting reservoir petrophysical attributes s. Pdf spe177709ms evaluation of water saturation in a. Low resistivity and corrosivity are inversely related. One of the main causes resulting in lrp zones, especially in carbonates, is the. Traditionally, resistivitybased logs are used to identify pay intervals based on the resistivity contrast between reservoir fluids.
Low resistivity pay zones have baffled many log analysts for years. Typical generally admissible porosity values for an oil reservoir range from between 10% and 25%, with porosity values of above 25% desirable 1. Advanced petrophysical approach for characterizing low. This is because conventional petrophysical interpretations are unable to identify pay intervals in lowresistivity reservoirs. Porescale network modeling of microporosity in lowresistivity pay zones of carbonate reservoir. Identifying, evaluating and commercializing lowresistivity, lowcontrast lrlc bypassed pay is a challenge. Resistivity image and conventional logs, are used to. Delivers excellent vertical resolution in lowresistivity, thinlybedded formations in boreholes from 334 to 30 inches.
The intricacy in the estimation of accurate hydrocarbon saturation is owed to their complex and heterogeneous pore structures, and mineralogy. Carbonate low resistivity pay formation evaluation workflow. This paper deals with the case of shaly sand formation as a low resistivity pay zone. The fo rmation in the salman field is divided into three reservoir zones and. This paper discuss the different reasons sandstone reservoir can have low resistivity. The pay zone includes carbonate reservoirs that resistivity logs have a. Low resistivity reservoir has certain conditions and regularity. The causes are usually quite simple but we often have to twist our mindset a little bit. The pay zone includes carbonate reservoirs that resistivity logs have a resistivity between 6 to 1 ohmme ters and even in some intervals reach less than 1 ohm. Pdf spe182912ms evaluating a complex lowresistivity.
Reservoir characterization of carbonate in low resistivity pays zones in the buwaib formation, persian gulf article pdf available in open journal of geology 0709. Low resistivity bitumen pay, pike field, athabasca oil sands. To detect a potential an lrp interval in a carbonate reservoir, i use these six generic indicators to detect a potential lrp interval. If the latter scenario, which carbonate rocks are permeable enough to migrate oil from. Evaluation of low resistivity beds using nuclear magnetic. The low resistivity pay could also partly be due to the geometri. Expert interpretation of reservoir saturation data boosts. The model is based on resistivity index ri curves measured at ambient and reservoir conditions, on double or triple porosity micritic and oolitic carbonates. Diagenetic controls on porosity and permeability in carbonates. Spe182912ms evaluating a complex lowresistivity pay carbonate reservoir onshore abu dhabi.
The approach acknowledges that a reservoir rock is a coupled. High water saturation, but zero water production in your. The porosity or percentage pore volume of reservoir rocks can be measured from well cuttings, core samples from drilling or wireline well logs. The concept of causes for lowresistivity and low resistivity contrast pay have been enriched over the years. Even resistivity independent saturation evaluation has been proposed through the use of. We used the fast resistivity index measurement frim method to obtain accurate and continuous ri curves down to very low water saturation 5%. Crains petrophysical handbook low resistivity pay zones. Conventional formation evaluation is limited in such complex micritic carbonate reservoir as the results is misleading the interpreter so the presented workflow will help to overcome these challenges and provide a simple technique with. Conventional openhole welllog gamma raydensityneutronresistivity analysis results are not conclusive for reservoir characterization of such a complex reservoir. Carbonate sediments can be deposited in many geological.
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