Well and Reservoir Surveillance/Management in a High Oil Price World

H.E.Y.B. Pehin Dato Yahya Bakar, Minister of Energy in the Brunei Prime Minister’s Office, and Grahaeme Henderson, Managing Director, Brunei Shell Petroleum Co. Sdn. Bhd., set the stage for the SPE Applied Technology Workshop (ATW) on “Well and Reservoir Surveillance/Management in a $60/bbl Oil Price World.” The ATW was held in Bandar Seri Begawan, Brunei, in March and was attended by 59 participants, representing 30 different organizations from 10 countries.

H.E.Y.B. Pehin Dato Yahya Bakar

Helping operators to achieve the right balance between short-term production gains and long-term development interests was the objective of the comprehensive technical agenda. Case studies and practical applications were presented in the following sessions: Well and Reservoir Surveillance/Management in Field Development Planning, Well and Reservoir Surveillance/Management, Case Studies/Lessons Learned, Field Operations and Organization, and New Technologies. There was also a breakout session and a poster session.

Increasing Value in Brownfields

The value of integrated full-field reviews was emphasized during ATW discussion. It was pointed out that proper data gathering and quality of the data play a critical part in the review process. And, in the case of production sharing contracts, maintaining continuity from operator to operator is of prime importance. A wide range of recovery factors were presented, and it was suggested to use analogs to assess realistic recovery factors.

Reservoir-Monitoring Issues

In a high-oil-price environment, many well/reservoir surveillance activities can be seen as costly to operators. During this session, discussion from the standpoint of overcoming the legacy of a low-cost mindset included production of heavy oil and emulsions from subsea developments. It was pointed out that subsea production almost always represents a high operating cost. Particular challenges are pipeline sharing and the associated tariff/production allocation, sand/emulsion production (specifically, the emulsion problem is a complicated one because the physics of conventional multiphase meters is not valid, and therefore, these are unreliable). Other techniques, such as the use of flow and nodal analysis, are not entirely satisfactory because proper testing and metering are still required to support the model. The need for accurate metering of emulsion flow for subsea production is significant.

Surveillance in the Minas Field

Because of the mature status of the field, the surveillance and management approach has moved from a fieldwide to a more-detailed reservoir approach in order to be effective. The Minas field is the largest waterflood field in southeast Asia, producing at ≈98% water cut with a current recovery factor exceeding 50%. Production is 100,000 BOPD, and the associated water production is ≈5 million B/D. A policy of zero discharge has been implemented in the field since 1997.

It was shown how a predictive model is used together with validation from actual field data for reservoir and well management. Pressure measurements are taken twice a month in 50 dedicated observation wells, and production log tests are used for production allocations. Microgravity, x-well tomography, and geochemical fingerprinting are techniques now being implemented in this field.

Reducing Planning Uncertainty

A mitigation plan implemented in the Betty field that resulted in a 100% increase in reserves was examined. On production since 1998, the Betty field has 28 wells draining approximately 22 reservoirs. Key uncertainties include fault positions and transmissibility, both tied to well performance, relative permeability curves, the use of hysteresis, and the permeability/porosity relationship. The mitigation plan used stochastic simulation models calibrated with logs and history matched to fully assess the impact of uncertainties.

Grahaeme Henderson

Case Studies

Brunei Shell Petroleum Land, Field, Well, and Reservoir Management. The most mature field in Brunei, the Seria field, is a stacked-reservoir system with more than 500 reservoirs and 800 wells. It was explained how weekly well-review activities result in identification of opportunities; the data gathered feed reservoir reviews that result in identifying further development opportunities. Fit-for-purpose technologies, such as low-cost distributed temperature sensing and the “gecko” well concept, are being applied. A low-cost well-abandonment technique also is being applied in a sustained fashion to manage the large number of closed-in wells effectively.

Minas Reservoir Pressure Reduction and Dual Processing: Alternatives To Operate Efficiently and Improve Production. In this field with 98% water cut, performance improvement is focused on existing base assets, including surface and subsurface challenges, the need to maintain zero discharge, and expense of upgrades. It was noted that reservoir-pressure reduction is expected to impact recovery. The effects of considering alternatives or maintaining current status were argued. The possibilities of reducing reservoir pressure, optimization with dual processing, and assessing the impact on oil recovery were also discussed.

It was noted that an integrated review for determining target and potential, a dual completion with inflow regulator, appropriate surveillance, and an intelligent completion that mechanically regulates flow from each layer will be required. In tight-reservoir conditions with injection, imposing the required drawdown is an issue.

Permanently Installed Real-Time Surveillance Using Fiber Optics and Distributed Temperature Sensing (DTS). Examples of permanently installed systems (in which temperature sensors are positioned at 1-m intervals) were introduced, and comparisons were made between single-ended and double-ended completions. An example from China’s Bohai Bay featured an electrical-submersible-pump system. At pump startup, a correlation is made between the DTS and the resistivity log, giving confidence in cleanup and enabling change monitoring. Once on steady state, the model is used to backout a flow profile. The second example presented involved a thermal model used to optimize reservoir pressure. Crossflow between wells was seen under shut-in conditions, and the use of temperature information offered a quantitative idea of water inflow.

The 12-member ATW Program Com-mittee was cochaired by Sin Fah Yap from Brunei Shell Petroleum Co. Sdn. Bhd. and Stephen Sakowski from Baker Oil Tools. Committee members included Amiruddin Hj. Abdi Manaf, Petroleum Unit, Prime Minister’s Office; Ellynah Abdul Rahman, Brunei Shell Petroleum Co. Sdn. Bhd.; Hj. Jameel Ahmed Hj. Basheer Ahmed, QAF Energy Support Services Sdn. Bhd.; Boy Esvano Idroos, Total E&P Indonesie; Angela Jamieson, Brunei Shell Petroleum Co. Sdn. Bhd.; Ekrem Kasap, Schlumberger; Richard Paparde, Halliburton; Daniel Saenz, Schlumberger; Magdalene Sikun, Brunei Shell Petroleum Co. Sdn. Bhd.; and Shi-Yi Zheng, Heriot-Watt U.