"Mature" fields today account for over 70% of the worldwide oil and gas production. In view of the increasing global demand for fossil fuels during the next decades, it is the task of the E&P industry to develop innovative and cost effective technologies to substantially increase the rate of recovery from today's average of 35% to over 50% for oil and from about 70% to over 80% ultimate recovery for gas. To achieve this goal it will be necessary to optimise the efficiency of operation and maintenance while minimizing environmental impact. In addition to the exploitation of new technologies the industry needs to be open minded for modern management techniques and new business models in order to keep control of the technical and economic risks. The successful integration of various new technologies will have a major effect on the reserve renewal rate as 1% increase in recovery would provide an additional 2 years of supply. Main focus will be on the presentation of the giant and mature Altmark gas field - with 9.4 Tcf GIIP the biggest gas field in Germany - which has currently reached a recovery factor of 78%. It will be shown how the operator, EEG, is applying various technologies and an alternative business model to constantly increase the field life and hence reserves. Due to the field specifics, e.g. high temperature, constantly decreased reservoir pressure and high formation water salinity, the main operational challenges the operator is facing are rock stability, water lifting, scales removal and remediation of formation damage, a variety of reserves development and maintenance methods are applied like sidetracks and chemical treatments with surfactants and polymers, respectively. Apart from presenting the range of well treatment and monitoring technologies, another important topic which will be presented in this paper is the economic approach to efficiently handle the compartmentalised brownfield reservoir and production issues that allow the expected ultimate recovery to exceed 80%. Introduction Over the last decade, the oil and gas industry - apart from the need of replenishing reserves through exploration activities- has put increasing efforts into the development of a variety of new technologies to unlock reserves in mature fields (mature fields are generally defined as oil and gas fields in a state of declining production having passed their peak production level according to the ATW on "Field Management of Mature Reservoirs", often synonymous to brownfields). This is simply due to the circumstance that 67 to 72%[1] of today's hydrocarbon production originate from this field category and hence represent a significant resource for the worlds increasing energy demand. Besides the need to introduce advanced technologies, the oil and gas industry has been also facing the challenge to increase cost efficiency of their maturing assets in order to compensate for the declining production level and the high level of fixed costs. This paper is intended to present a brief overview of the different approaches the operators of mature fields have taken in order to increase ultimate recovery beyond average. The main focus will be on the presentation of tools EEG has been applying in the giant Altmark gas field—both the successful and unsuccessful ones—in order to increase recovery beyond 80%. In addition it will be demonstrated which recent but yet untested technological and business approach EEG is taking to potentially extend field life.

This study suggests a robust multiple realization approach to determine optimum production stimulation strategy. Unlike the majority of existing similar studies, the suggested approach concentrates both on geological uncertainties and improving of hydraulic fracturing modeling. Existing similar studies either concentrate on the reservoir uncertainties (i.e., ignoring the importance of hydraulic fracturing simulation and calibration), or vice versa, concentrate on the sensitivity of the hydraulic fracturing parameters (i.e., ignoring the wide range of geological uncertainties). The key feature of the suggested approach is the use of a single platform for static geological model, hydraulic fracturing simulator, and hydrodynamic modeling. The study shows the example of suggested approach implementation on one of the complex oilfields in Western Kazakhstan, where approach helped to determine the probability of stimulation success and allowed to determine the optimum stimulation strategy.