A deep German onshore Rotliegendes gasfield in a complex sedimentary and structural environment is subject to evaluation of the remaining potential for additional wells and possible recovery acceleration. A graben structure filled with aeolian sediments in an overall depth of about 4900m comprises the dry gas bearing reservoir. The field is developed by a limited number of expensive wells with a relatively wide well spacing. The wells face complicated drilling conditions and a necessary deviation to honour environmental issues which severely limit the number of well site locations. The quality of the 3D seismic is limited because of Zechstein salt intrusions in the overburden. Hence the structural and interpreted fault models are subject to significant uncertainties. Characterisation of aeolian sedimentary facies distribution and quality, which suffers from diagenetic effects, is achieved by a geostatistical approach. The model is mainly based on information from cores and logs. Seismic information could only be used to guide the distribution of the aeolian reservoir facies and a probably unproductive fanglomerate facies type. One main question is the level of compartmentalisation of the field due to faults and flow barriers related to reservoir facies distribution. During the dynamic modelling process possible scenarios are checked against the observed production data regarding communication and GIIP distribution. This gives a range of possibilities leading to a significant uncertainty regarding the prediction of future production and the effect of acceleration wells. There is room for only a few more wells. The decision where to place these is supported by the integrated modelling approach. This has been chosen to address a wide range of uncertainty of both static and dynamic effects. The static effects have been addressed by a combination of geostatistical static reservoir modelling with fully 3D static uncertainty estimation. The basis for the dynamic modelling part is a family of realisations defined by a process to identify "most diverse" representative scenarios out of bigger number of geological realisations. Computer aided history matching, experimental design and proxy solutions gave a very effective approach to handle the uncertainty estimation with the dynamic reservoir simulation. The fully integrated workflow allowed an optimized process to estimate the uncertainty of prediction within a limited time frame. The main subject of this paper is the process of dynamic reservoir simulation using these techniques and discussion of the results. Introduction The main weakness associated with modeling which utilises a detailed reservoir description to reproduce observed dynamic behaviour is the ill-posed nature of the inverse problem for which a solution is sought. The non-uniqueness of solutions 1 in this field of complex inverse problems is well known in the industry 2,3,4. Sparse control data burdened with uncertainty, measurement errors and questions about representativeness in almost all cases lead to highly non-linear responses. It is seldom the case in reality that only one unique history match (HM) solution exists; typically examples where this appears to occur are either synthetic, obviously highly constrained or extremely simple 5. Traditionally this generic problem has been more or less ignored (at least in the daily business of the reservoir modeling workflow), primarily due to cost in terms oftime andhardware. In the early 1990s the concept of the Shared Earth Model 6 lead to a stepwise integration of more and more data on an increasingly detailed level. Availability of cheap computing power coupled with sophisticated software applications has lead to increased complexity in the static reservoir models, leading to the requirement to upscale to a simulation scale to perform any form of dynamic modeling at all in a practical timeframe.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA deep German onshore Rotliegendes gasfield in a complex sedimentary and structural environment is subject to evaluation of the remaining potential for additional wells and possible recovery acceleration.

In May 2019, the merger between Wintershall GmbH and DEA Deutsche Erdoel AG was closed, which was the start of Wintershall Dea.This paper provides detailed insight into managing reserves and resource information during this merger. After merger, three resource management activities required attention: (i) combining existing resources reporting, (ii) defining a lean but effective resources management and control system, and (iii) ensuring readiness for Initial Public Offering (IPO) by establishing an external independent evaluation of resources ("external resource audit"). This paper describes objectives, challenges and solutions on reserves and resources reporting of the new company. The merged reserves and resources database of the previous year's reports had to consider audits from two different reporting systems in parallel to four different external auditors.With priorities defined by status of external auditing, operatorship and asset share a common database was derived and could immediately be used for financial transactions such as the issuance of an inaugural bond. The new system for internal reporting of petroleum resources provides a fit-for-purpose approach, such as a consistent interpretation of commerciality criteria or definition of resources sub-classes.Particular attention was paid to synergies with respect to business planning, strategic portfolio analysis, and a link to technology & innovation. By defining specific attributes and sub-processes, the portfolio can be analyzed systematically. This provides additional insights and ensures synergies with business planning, strategic planning as well as internal technology initiatives. A systematic resource control system is defined focusing on internal review, external and internal audits as well as synergetic use of project reviews. Moreover, a feedback loop for continuous improvement of reservoir management allows attending to important audit observations. The external resource audit to ensure IPO readiness was structured to assign tasks for head office, business units and auditing company.The sequence of events from introduction to assets to reconciliation of differences between auditor and company was set-up, executed and monitored.Focus was on the definition of a structured but agile approach for external independent evaluation of all reserves and contingent resources.