Key reservoir-testing issues examined by workshop

Eighty-seven participants, representing 48 organizations from 25 countries, attended the SPE Applied Technology Workshop (ATW) "Reservoir Testing in a World of High Production Values," held 11-14 December 2007 in Bali, Indonesia.

The ATW comprised 11 sessions, including the keynote address by Tri Siwindono, Chief Executive Officer, PT Pertamina. Siwindono focused on the value of information obtained in reservoir testing and noted that in the current environment of high production values, Pertamina rarely tests oil wells because of the cost of lost production. Most of his company's reservoir tests involve gas wells. He highlighted oil-producing countries' desire to find cost-effective and environmentally protective reservoir-testing methods.

Session 2, chaired by Florian Hollaender, Schlumberger, and Bob Hite, Shell, dealt with new technologies and their applications. Henk Kool, Halliburton, made a presentation on a new bottomhole drillstem-test (DST) -conveyed sampling system. By use of this low-cost system, representative samples are captured under controlled timing and are overpressurized by means of a nitrogen cushion as they are carried to the surface, ensuring that the samples remain representative.

Bertrand Theuveny, Schlumberger, discussed the current and possible future use of multiphase flowmeters (MPFMs). Of the more than 3,000 MPFMs currently deployed worldwide, including 150-200 mobile units, less than 400 are used regularly for well testing. MPFMs have yet to attain full acceptance by operating companies, Theuveny said. Challenges affecting the wider use of MPFMs, he indicated, include the economic limitations of metering low flow rates; bringing accurate multiphase-measurement technology downhole, as opposed to conducting metering at the surface only; making full use of the transient-rate information obtained from these meters; and data-reduction issues related to permanent meter installations or long-term tests.

Ichiro Shikano, Nippon Oil, presented a case study in which a naturally fractured basement reservoir offshore Vietnam was characterized with a combination of pressure-transient tests with tracers. The reservoir-management objectives call for avoiding gas and/or water breakthrough. Water injection is used to manage the gas/oil and oil/water contacts, a challenge in the highly heterogeneous fractured configuration. To assess interwell communication, different tracers were introduced through injectors in different parts of the field, enabling a simple estimation to be made of the source of the water. Although the data-acquisition scheme did not resolve all uncertainties, the simulation model was updated on the basis of the interwell communication results, and a better history match was achieved.

The third session, chaired by Roland Horne, Stanford University, and Olivier Houz, Kappa Engineering, focused on permanent downhole gauges (PDGs) and data mining in particular, the interpretation of the data that are recovered from the gauges. Hite described how PDGs had been used to determine the distribution of skins as a function of time during the development. The PDG data also were used to estimate how permeability-thickness changed as the project life continued. Suwat Athichanagorn, Chulalongkorn University, summarized methodologies for the preparation and analysis of the data that are recovered from PDGs. Bay Chun Yong, Talisman, Malaysia, described how PDGs were deployed in his company and the uses to which the data were applied. PDG data are widely used in Talisman for reservoir-surveillance and -management applications, including pressure monitoring and control, interference testing, water-injection monitoring, well transient testing, evaluation of well performance, and history matching in reservoir-simulation models.

Session 4, chaired by Mariam Aziz, Petronas, and Medhat Kamal, Chevron, addressed dynamic surveillance/automatic analysis. Vijay Prothapragada, Occidental, discussed a dynamic-surveillance system successfully implemented in the Idd El Shargi North Dome field in Qatar. The system consisted of MPFMs installed on 80% of the production wells, PDGs installed on 70% of the production wells, well models built for every well, a supervisory-control-and-data-acquisition system providing real-time monitoring data from all the wells and MPFMs, and a network model of the wells and complex pipeline network. All of these components are needed, Prothapragada said, because each module validates the other through the integrated daily-production-surveillance system.

Lumay Viloria-Gomez, Schlumberger, described the integration of PDG data in ways useful to the production engineer. One solution she described is a screening process built in a common framework that enables identification of events, alarms, and notifications; provides appropriate filtering and transient identification using a wavelet method; allows rate reconstruction; and enables systems identification by use of deconvolution. After the first model is set up, models used in subsequent transients are validated automatically. A fast, gridless semianalytical computation that handles multiple wells and layers is used for inversion (parameter estimation).

Tokunosuke Ito, Zedi, described a server-based network-surveillance and data-storage system, already implemented in operations in Alberta, Canada.

The fifth session comprised the poster presentations and was managed by Kazuyoshi Arisaka, Japan Oil. Six presenta�tions were given in all. Hisham Zubari, Bapco, gave a presentation on the use of an analytical multilayer model for well-test interpretation on gas wells in the Awali field of Bahrain. A presentation by Kool dealt with high-pressure/high-temperature (HP/HT) qualification testing of DST tools. Saifon Daungkaew, Schlumberger, discussed injection-falloff tests in deepwater reservoirs. Valeriy Iktisanov, Institution Tatnipineft of JSC Tatneft, gave a presentation on the pressure-curve interpretation of multilateral wells. A presentation by Mike Brunton, Expro Group, covered enhanced measurement for surface well testing. Robert Buchanan, Expro Group, gave a presentation on limited-entry testing.