In 2014, TOTAL performed two Single Well Tracer Tests (SWTT) to evaluate the remaining oil saturation in an offshore high temperature, high salinity carbonate reservoir. The SWTT method has proved to be a reliable way, when carefully programmed, to measure a representative remaining oil saturation without being impacted by near wellbore effects. The objective of these measurements was to evaluate the efficiency of a single well chemical EOR (CEOR) pilot by measuring oil desaturation.
Extensive in-house laboratory work was carried out by TOTAL to lay the foundation for the pre and post CEOR pilot SWTTs. A specific tracer injection skid was internally developed to ease the operations. Specific numerical work was performed to achieve robust designs and interpretations. These simulations, carried out in-house, took into account all major uncertainties highlighted by experimental work. Detailed results from the SWTT preparation phase will be described in the paper.
Results from the baseline SWTT interpretation evidenced excellent quality tracer profiles from the first test and high remaining oil saturation, improving our knowledge on the flooding pattern of this reservoir. Results from the post EOR SWTT showed again a clear response of a remarkable decrease in remaining oil saturation, proving the efficiency of the chemical formulation provided by TOTAL and the envisaged recovery mechanism. Interpretation of these Single Well Tracer Tests also allowed us to evidence a much lower than anticipated reservoir dispersion. These findings highlight the potential of EOR implementations in these carbonate formations.
Lessons learned from these two offshore SWTTs are discussed in this paper, such as the need for specific preparation to tackle the complexity of a high temperature high salinity carbonate reservoir in presence of H2S. TOTAL has shown that such operations can be performed in a strict timeframe while adhering to company safety rules. Careful interpretation of such results is mandatory to validate the success of the single well chemical EOR pilot.
Al-Amrie, Omar (ADNOC) | Peltier, Sophie (ADNOC) | Pearce, Adrian (ADNOC) | Abu-Dhabi, Total (ADNOC) | Al-Yafei, Arafat (ADNOC) | Morel, Danielle (Total SA) | Bourrel, Maurice (Total SA) | Bursaux, Romain (Total SA) | Cordelier, Philippe (Total SA) | Jouenne, Stephane (Total SA) | Juilla, Hugo (Total SA) | Klimenko, Alexandra (Total SA) | Levitt, David (Total SA) | Nguyen, Michel (Total SA)
In 2014, Total performed a surfactant-polymer single-well pilot to test the effectiveness of a surfactant formulation developed in-house, and including a new proprietary class of surfactants with improved temperature- and salinity-tolerance characteristics. This paper unveils the results of this pilot which targeted a high temperature, high salinity carbonate reservoir. The operations were performed on an oil bearing reservoir of Lower Cretaceous age, in an offshore field operated by Total since 1974 and located 180 km offshore Abu Dhabi. Dedicated topsides were designed and installed for this EOR project. Extensive in-house laboratory studies were performed to select and synthesize the chemicals. Specific simulations, using laboratory results as input, were carried out to predict the pilot performance, design the Single Well Tracer Tests (SWTTs), and size the equipment.
In this paper we will discuss the workflow used to select the most appropriate well and present the methods and results used to characterize the reservoir. Then we will relate it to the surfactant-polymer injection field operations. Finally the reservoir monitoring activities that were necessary to preserve reservoir integrity and demonstrate the pilot efficiency will be described.
The strong decrease in remaining oil saturation measured after the chemical EOR pilot clearly proves the effectiveness of the chemicals synthesized by Total to mobilize the remaining immobile oil after water-flood.
These positive outcomes change the perception of CEOR in hot, saline Middle-East carbonate reservoirs, and could be a "game changer".
The application of the Carbon Dioxide Enhanced Oil Recovery (CO2-EOR) to an offshore oilfield in Vietnam has been investigated through an international joint study between Japan and Vietnam since 2007. In order to reduce and mitigate uncertainties and risks for future field scale application, a CO2-EOR pilot test was conducted in the Rang Dong field, offshore Vietnam in 2011.
The pilot test was conducted as a single-well "Huff-n-Puff?? operation which was designed to minimize the test duration, required CO2 volume to observe the meaningful CO2-EOR effects and to reduce the risk of corrosion to the existing facility. Over 100 tons of CO2 were successfully injected into the Lower Miocene sandstone reservoir and the well was flowed back after two days of soaking time. Various parameters were monitored including production rate, bottom-hole pressure and production fluid properties. To investigate the CO2-EOR effects and for the purpose of monitoring the reservoir fluid saturation change, cased hole pulsed neutron saturation logging was carried out during every stage of the test. These logging operations and their timing were carefully designed to avoid any possibility of fluid contamination and to minimize operation time.
Through the analysis of the acquired logs, vertical contrast of preferential CO2 injection, zonal oil saturation change, oil saturation change with time within single run, etc., were clearly identified. These observations played important roles in evaluating the CO2-EOR effect in detail by comparing them with the reservoir simulation prediction.
In this paper the detailed design for the reservoir fluid saturation monitoring, observed results and three-phase fluid saturation changes wtih time are discussed.
This paper focuses on the design, the operation and the laboratory work needed for performing a successfull Single Well Tracer Test (SWTT) campaign in the Handil mature field Indonesia. Three tests have been performed in different waterflooded reservoirs to assess the repartition of Remaining Oil Saturation (ROS) in the field.
An extensive laboratory work has been performed prior to tests to screen chemicals that could be used and then to measure the two main parameters needed for the design of the tests: the partitioning coefficient of the primary tracer between water and oil (Kd) and the hydrolysis reaction rate (kH) of the primary tracer into the water. Measurements were performed at reservoir temperature and pressure conditions using recombined live oil sample and recombined brine with respect to the salinity of each reservoir. Results indicate very low discrepancy of Kd value between reservoirs (4 to 5), while kH show a strong linear dependency with salinity (from 0.12 to 0.45 day-1). To take into account the presence of trapped gas saturation, we measured also the partitioning coefficient of AcOET between the water and the gas phase at reservoir pressure and temperature. As expected the Kd water/gas was low compare to the water/oil with a value of 0.5.
Tests were performed in parallel after the installation and the calibration of laboratory equipments and the commissionning of the injection barge. The tracer profiles quality recorded from the three tests was very good with high tracer recovery and low scattering data. However the interpretation was challenging, and numerical simulation was necessary to handle non ideal phenomenan occurring during these tests and to get reliable ROS estimation. The ROS values range between 20-30% which allows moving forward in the identification of potential EOR reservoir candidates and locations of future pilot zones for the more promising EOR processes.