Understanding the Flow Dynamics of CO2 Plumes in the Subsurface

There are several significant differences between the behavior of injected CO2 and reservoired hydrocarbons in the subsurface. These fundamental differences greatly influence the modeling of CO2 plumes. Carbon capture, utilization, and storage (CCUS) is growing in importance in the exploration and production (E&P) regulatory environment with the Oil and Gas Climate Initiative (OGCI) making CCUS a priority. Companies need to prospect for storage sites and evaluate both the short-term risks and long-term fate of stored carbon dioxide (CO2). Understanding the physics governing fluid flow is important to both CO2 storage and hydrocarbon exploration and production. In the last decade, there has been much research into the movement and migration of CO2 in the subsurface. A better understanding of the flow dynamics of CO2 plumes in the subsurface has highlighted a number of significant differences in modeling CO2 storage sites compared with hydrocarbon reservoir simulations. These differences can greatly influence reliability when modeling CO2 storage sites.

BIOSTRATIGRAPHY AND SEQUENCE STRATIGRAPHY OF THE DEEP OFFSHORE NIGER DELTA AND IMPLICATIONS FOR FUTURE HYDROCARBON EXPLORATION IN THE PALAEOGENE SEQUENCES

The Niger Delta Deep Offshore Basin has been the latest frontier within the Niger Delta for hydrocarbon exploration and production activities. Until the onset of drilling activities in the early nineteen nineties, little was known about the biostratigraphy of this frontier setting. Thus, uncertainties existed in the ages ascribed to the various stratigraphic sequences. Presently, several wells have been drilled in the Deep Offshore Niger Delta and a three-pronged biostratigraphic data and some sequence stratigraphic interpretations have become available. We integrated biostratigraphic data comprising palynological, foraminiferal, and calcareous nannoplankton zonation and biofacies, wireline log information and regional-3D seismic data, with simple basic sequence stratigraphic analysis for a detailed well correlation, regional mapping of hydrocarbon-bearing intervals, and evaluation of the thicknesses of promising stratigraphic intervals. Results show a significant effect on not only the earlier conceptualized age of the deepest prospective reservoirs, but also the ages of possible source rocks in the Paleogene of the Niger Delta Offshore sequence. This finding will help in the realistic assumptions of source rock characterization, charge modeling/prediction, and the stratigraphic thicknesses of the offshore sequences and their reservoirs. This paper examines the specific derivable age interpretations from the integration of at least six wells, biostratigraphic data with seismic and the implications of these interpretations for hydrocarbon prospectivity of the Paleogene sequences. Furthermore, this paper documents the biostratigraphy work done in the area, in all the structural belts where drilling has occurred including the deepest well drilled in the Deep Offshore Niger Delta, Bosi-006. The results of this study have a critical impact on the current regional geological understanding of the Deep Offshore Niger Delta.

Comparison of Hydrocarbon Fiscal Regimes of Some European Oil and Gas Producers and Perspectives for Improvement in the Republic of Croatia

Hydrocarbon exploration and production activities are basic to the functioning of the oil and gas industry, while concession contracts and fees are central concepts in the aforementioned activities. The authors consider several questions regarding these concepts, such as: what is the legislative, institutional, and fiscal framework in certain European countries regarding hydrocarbon exploration and production? What are the major differences between them? Finally, is there room for improvement of the framework in the Republic of Croatia? To answer these questions, the authors contacted some of the relevant institutions and accessed official government gazettes, institution websites, legal aggregators, journal articles, books, and different legal publications regarding the oil and gas industry for several European countries, namely the Kingdom of Norway, the Russian Federation, the Republic of Austria, and the Republic of Croatia. As a result, this paper presents an overview of legislation, institutions, concession contracts, taxes, and fees for each of the aforementioned countries. The authors conclude that the Republic of Croatia could benefit from applying some foreign solutions in its own legislative and fiscal framework, i.e., using a sliding scale for royalty calculation and simplifying some administrative procedures.

Into the Benthos and Back: What have Infauna Taught Us

ABSTRACT ID 685153 Because of death and gravity, the bottom of the sea is the memory of the ecosystem, where a record of all past events can be found as you move into deeper layers of sediment. Thus, benthos are primary indicators for environmental assessments. As hydrocarbon exploration and production moved to deeper waters, so did environmental studies. But there were only a few Gulf-wide surveys in the deepest parts of the Gulf of Mexico, and our understanding of deep-sea processes was based primarily on other regions of the world. The intensive focus on deep-sea response during and after the Deepwater Horizon (DWH) accident increased our knowledge dramatically. We learned that the deep sea is dynamic, fragile, and will take a long time to recover. There was a 50% loss of biodiversity within 9 km diameter around the DWH site, and a 10% within a 17 km of the site. But there is still much to learn. The deep-sea is a reservoir of biodiversity on Earth, but about 60% of Gulf of Mexico taxa are still unknown, which is a major hinderance to understanding the effects of oil spills. The northern Gulf of Mexico is dominated by Mississippi River outflow, but exactly how it drives deep-sea dynamics needs better resolution. Two outcomes of the last decade of research is that we know benthos diversity is a sensitive indicator of environmental change and damage, the surface sediments are the biologically active zones, and the natural process of sinking particles will eventually cover the damaged sediment leading to natural recovery. This “restoration in place” strategy must be confirmed by future monitoring and assessment studies.

Multichannel systems in an ancient river-dominated delta: case study of the lower Yanchang Formation, southwest Ordos Basin, China

Distributary channels in large deltas can form a channel pattern similar to braided fluvial system or anastomosed fluvial system that have multichannel systems. Although both systems are of generally comparable platforms, their geometry, sedimentology, and facies associations may exhibit unique characteristics. Many ancient multichannel systems have been interpreted as braided patterns, but some are certainly anastomosed patterns. A reevaluation of ancient multichannel architectures and sedimentology patterns is needed to improve discrimination of braided and anastomosed patterns of multichannel systems. This study examines the characteristics of two modern anastomosed pattern channel systems. Those modern systems are compared to ancient examples in the lower Yanchang Formation, southwest Ordos Basin. This comparison indicates that the multichannel systems of the delta, southwest Ordos Basin, exhibit greater similarity to modern anastomosed channel systems of shallow-water deltas. Systems of low-sinuosity distributary channels and interdistributary bays or swamp islands are developed mainly between the channels, and there are no mouth bar deposits. Both modern and ancient multichannel systems suggest that low gradient slope is a significant controlling factor in the formation of anastomosed pattern channels in river-dominated deltas. The identification of anastomosed patterns plays a significant role in reservoir characterization and hydrocarbon exploration and production in delta systems.

A Critical Review of Rules and Regulations for Permanently Plugged and Abandoned Wells

Permanent Plug and Abandonment (P&A) of wells has been an inevitable part of hydrocarbon exploration and production; however, the methodology has not evolved with the same pace as the rest of the industry. Nonetheless, after the environmental impact of some recent events including the Deepwater Horizon oil spill, permanent P&A of hydrocarbon wells has been receiving more attention. Accordingly, regulatory authorities who oversee the P&A activities and operators have tried to improve the pre-existing P&A methodology by defining a modern P&A philosophy, zero leakage criterion. Although the legislated criterion, adapted by most authorities, has challenged the industry and it had a constructive impact on P&A operations, due to technology deficiencies, the associated cost of operation has significantly increased. In this work, most of the publicly available regulations and their recommended practices addressing P&A have been reviewed and discussed. The focus has been given to zero leakage acceptance policy, conventional versus risk-based approach, barrier verification, human factor in P&A, and technology deficiencies. Although Norway is not a major hydrocarbon producer based on the daily production rate, but because of its stricter requirement on P&A, its recommended practice (NORSOK D-010) for P&A has been used in different oil producing countries. As P&A and its impact on environment is a transnational subject, it is suggested to formulate an international guideline or standard on P&A, given the fact that every well is unique when considering P&A operation.