THE GEOLOGY AND HYDROCARBON POTENTIAL OF THE PEEL AND SOLWAY BASINS, EAST IRISH SEA

Data from recent exploration campaigns by Elf Exploration UK plc and partners in the Peel and Solway Basins (East Irish Sea) have provided significant new information on the geology and hydrocarbon potential of these previously unexplored areas. In this paper, I present a regional geological framework for the basins based on outcrop studies, potential field data and regional seismic lines. The dominant NE-SW and NW-SE structural trends are probably inherited from the Caledonian Orogeny and show evidence of repeated reactivation. Seismic interpretation indicates that the NE-SW trending faults were important in controlling Early Carboniferous basin development, and that transpressional movement along these faults in response to N-S compression led to basin inversion during the Variscan Orogeny. New well data indicate that both the Peel and Solway Basins were subjected to major erosion at this time, causing the entire Upper Carboniferous stratigraphy to be removed. Preserved Dinantian facies comprise shallow-marine sandstones, shales and carbonates in the NE, passing into shallow-water, high energy carbonates in the SW. A change to E-W extension during the Permo-Triassic led to renewed extensional motion on the underlying Caledonian faults, and to the creation of a new system of faults oriented N-S. The Permian and Triassic sections present in the wells in the Peel and Solway Basins are very similar to those in the numerous exploration wells in the East Irish Sea Basin to the SE. Liassic rocks are partly preserved in both the Peel and Solway Basins. The intra-basinal highs which separate the basins in this region are thought to have been initiated during Late Cimmerian uplift, and to have been enhanced by Laramide and Alpine phases of uplift. Laramide uplift was also accompanied by the emplacement of WNW-ESE trending dykes. Regional stratigraphic information has been combined with apatite fission-track data and vitrinite reflectance data to constrain these phases of uplift. These data suggest that at the present day, the Peel and Solway Basins are isolated remnants of a previously more extensive cover of Mesozoic rocks. The three exploration wells drilled in the Peel and Solway Basins by Elf Exploration UK plc tested valid Triassic fault-block traps, but failed to encounter any significant hydrocarbon shows. Variable, but generally good quality reservoirs exist at the top of the Sherwood Sandstone Group. The main control on reservoir quality is the primary sedimentological character of the sandstones, with cementation and compaction locally reducing quality. Over most of the area, evaporites and shales in the Mercia Mudstone Group form a viable top and lateral seal. The main factor preventing development of a viable petroleum system appears to be the absence of significant Carboniferous source rocks.     

Scattering by a multilayer chiral cylinder

An efficient recursive eigenfunction solution for the problem of scattering by a multilayer chiral circular cylinder, with or without a surface impedance center cylinder, is presented. For an M layer cylinder, the solution requires the multiplication of M4×4 matrices, versus the solution of a 4M×4M matrix equation in a standard approach. The problem of a transverse electric (TE) incident plane wave differs from that of a transverse magnetic (TM) wave only by a plus/minus sign at one step in the solution. The addition of the surface impedance center cylinder requires only one additional matrix multiplication. Numerical results, including echo width and internal fields, are presented for several sample cylinders     

Courseware review

Jeanie C. Crain is an associate professor in English at Missouri Western State College. She directs the computer assisted laboratory for writing instruction and teaches composition, literature, technical writing, and desktop publishing.     

Stable interaction control and coulomb friction compensation using natural admittance control

A new control system design formulation is presented for achieving high-performance, guaranteed-stable impedance control. While the bandwidth of the resulting controller is no higher than alternative techniques, the new formulation significantly improves performance when Coulomb friction is present in the system. The technique requires a careful choice of the target impedance. The resulting feedback compensators are causal and have stable poles, although they are often non-minimum phase. General rules for controller synthesis are derived. Experimental performance results are presented for a two-mass system with internal compliance and Coulomb friction. Results demonstrate that the technique is successful in rejecting internal friction force disturbances while maintaining a passive driving-point impedance. © 1994 John Wiley & Sons, Inc.     

Search adaptations and the challenges of the Web

Search has become a hot topic in Internet computing, with rival search engines battling to become the de facto Web portal, harnessing search algorithms to wade through information on a scale undreamed of by early information retrieval (IR) pioneers. This article examines how search has matured from its roots in specialized IR systems to become a key foundation of the Web. The authors describe new challenges posed by the Web's scale, and show how search is changing the nature of the Web as much as the Web has changed the nature of search.     

Hot-potato algorithms for permutation routing

We develop a methodology for the design of hot-potato algorithms for routing permutations. The basic idea is to convert existing store-and-forward routing algorithms to hot-potato algorithms. Using it, we obtain the following complexity bounds for permutation routing: n×n Mesh: 7n+o(n) steps; 2ⁿ hypercube: O(n²) steps; n×n Torus: 4n+o(n) steps. The algorithm for the two-dimensional grid is the first to be both deterministic and asymptotically optimal. The algorithm for the 2ⁿ-nodes Boolean cube is the first deterministic algorithm that achieves a complexity of o(2ⁿ) steps     

SQL Access: an implementation of the ISO Remote Database AccessStandard

As an enterprise begins tying heterogeneous systems into a single information system, it encounters the difficult task of interfacing different platforms running different operating systems, network protocols, and data management systems. Bringing all these elements together into a coherent information resource can require substantial effort and might result in a system that needs the interfaces reworked every time a new platform or product is introduced into the system. To address these issues, the International Organization for Standardization has drafted the Remote Database Access Standard to provide a protocol that can be universally accepted, implemented, and validated, and thereby provide users with a single, well-defined interface for heterogeneous environments. Based on a client-server architecture, RDA uses well-defined Open Systems Interconnect services as the basis for the RDA services     

A fundamental group for greyscale digital images

One of the concepts from topology that has found use in image processing is the so called Fundamental Group of an image. A definition for the digital fundamental group of a binary picture was introduced by Kong in A digital fundamental group [4]. This paper introduces a fundamental group for greyscale images. We also describe Poincaré's classical method for computing a representation of the fundamental group and extend this to work with our greyscale version.     

The cofactors required by C3 nephritic factor to generate a C3 convertase in vitro

The mechanisms by which a C3 convertase is generated by C3 nephritic factor (NeF) were investigated using purified NeF, C3, C3b, factor B and factor D of the alternative pathway of complement activation. NeF could generate a C3 convertase with C3 and B in the absence of D, and without cleavage of B. At lower concentrations of NeF the addition of D was required to generate a C3 convertase, and B cleavage now occurred. The generation of both the D-independent and D-dependent C3 convertases with NeF was inhibited by preincubation of the C3 source with C3b inactivator (KAF); isolated C3b was more efficient than the C3 preparations used in generating the D-independent C3 convertase with NeF. These experiments indicate that C3b is required for the formation of both convertases, and that the reaction occurring with apparently native C3 is due to trace amounts of C3b. It is concluded that the C3 convertase generated by NeF in the absence of D is C3bB (NeF), and that generated in the presence of D is the feedback convertase C3bBb. The relevance of these experiments to reactions which may occur in vivo is discussed.