I. Intoduction This paper is concerned only with rocks of accepted Dalradian age. I have, therefore, not taken into account formations lying south-west of the Loch Skerrols thrust, which include the problematical Bowmore Sandstone. The succession, which I think may be considered as proved, is identical with that put forward by Prof. E. B. Bailey in 1917; but it has been established in the present instance mainly by consideration of current-bedding and graded bedding in several members of the sequence. The significance of certain conglomerates on Beannan Dubh, however, has again been investigated. In the following pages it is intended to retain the stratigraphical nomenclature used by Prof. Bailey, and also to discuss formations put forward by other authors in terms of this nomenclature. The Dalradian succession in Islay and Jura, according to my determination, is as follows, the oldest rocks being at the bottom of the table :— 11. Ardmore and Laphroaig Quartzites. 10. Port Ellen Phyllites. 9. Scarba Conglomeratic Group. 8. Jura Slates. 7. Main Quartzite. 6. Dolomitic Group of North Islay. 5. Power Fine-Grained Quartzite of North Islay. 4. Portaskaig Conglomerate. 3. Islay Limestone. 2. Mull of Oa Phyllites. 1. Maol an Fhithich Quartzite. Since opinions on the geological structure of this area are many and varied, it does not seem out of place here to review and analyse very briefly

I. Introduction The original of this paper forms part of a Ph.D. thesis accepted by the University of Glasgow, and available for reference in the University Library. With the consent of the author, who went abroad in 1933, the text was recast by Dr. E. B. Bailey for publication, and the illustrations redrawn by Dr. W. J. McCallien. In the meantime, Dr. G. L. Elles in 1935 published a paper dealing further with south Tayvallich, and the island of Danna. Although the present paper was read to the Society by Dr. Bailey in 1936, publication was held over until the author could revisit and re-examine the Tayvallich and Danna exposures in the light of Dr. Elles's conclusions, which had differed materially from those expressed by the author. This was not accomplished until the summer of 1939. The investigation was originally pursued while the writer held a Carnegie Research Scholarship at Glasgow University. The rocks of the three areas, exclusive of dykes and superficial deposits, consist of sedimentary and igneous schists of Dalradian age. The sediments are grouped according to E. B. Bailey's classification as follows, in descending order both of age and superposition:— Of these formational names, three—Ardrishaig, Loch Avich, and Shira—are taken from parts of the Loch Awe district outside the scope of the present paper. The igneous rocks are grouped under the broad heading epidiorite. Lavas and breccias are strongly developed in the Tayvallich Group, and also in the lower part of the Loch Avich

Gas/liquid ratios (GLRs) typically increase later in the life of a sucker rod-pumped well, and unconventional reservoirs may have high GLRs from the beginning of production. How to handle that gas production is important for sucker rod pumps, as the efficiency is reduced when gas enters the pump. A project was undertaken to quantify several methods used to handle gas production with sucker rod pumps and the effectiveness of each. This project focused on three areas of design or operation intended to improve gas handling: Gas separator design: The sizing of downhole gas separators was reviewed, and steps were taken to match the pumping system with the proper separator. In cases where the separator was not pulled, the pump displacement was adjusted to ensure it was within the capacity of the existing separator. Where there was an opportunity to replace the separator, the design was modified to ensure the separator capacity matched the expected well production.Variable speed drives: Horizontal wells do not provide consistent inflow, but rather exhibit slugging behavior as portions of the lateral load up with liquid or gas. This makes pump-off control difficult with conventional rod pump controllers, which stop the pump completely when there is a lack of fluid at the pump. The performance of variable speed drives was studied to determine if continuous operation while adjusting the speed to accommodate slugging would improve production.Backpressure valves: Backpressure has been used as a method to improve the performance of wells with gas interference, but the benefits have been questionable compared to the negative impacts on equipment loading. Wells with elevated tubing backpressure were identified, the backpressure was reduced to line pressure, and the impact on performance was monitored.

For our present purpose the Craignish Area is considered to include the peninsula of Craignish and its adjoining parts, as shown in the sketch-map, Text-fig. 1.

Objectives/Scope The performance of artificial lift systems on horizontal wells is greatly influenced by both the volume of gas produced and the tendency for gas slugging. With a sucker rod pump (SRP) system, this behaviour leads to gas interference at the pump, reducing system efficiency and equipment run life. With an electric submersible pump (ESP), gas slugs can cause cycling of the ESP, which may significantly shorten its run life. A trial project was launched to evaluate the performance of two tailpipe systems that could be applied to both forms of artificial lift to achieve the following goals: Methods, Procedures, Process Two tailpipe systems were tested in a number of wells using both SRPs and one ESP for lift. The systems differ in both separator design and packer location. The first uses a conventional packer-style gas separator with a reduced inner diameter (ID) tailpipe extending below the separator and past the KOP. The second uses a specialty cyclonic separator with a reduced ID tailpipe, and the packer is located at the lower end of the tailpipe. Some of these installations are outfitted with downhole gauges (DHGs) measuring pressure and temperature at several points along the tailpipe. The DHGs recorded pressure at the tailpipe inlet, tailpipe outlet, pump intake pressure, and pump discharge pressure. This surveillance package allowed for real-time monitoring of the performance of both the tailpipe and the artificial lift system, while also providing data for modelling the flow regime through the tailpipe. The modelling results were used to forecast long-term performance of the system as the well production declines over time. Results, Observations, Conclusions Results from the field trial show the performance of each system from a variety of standpoints: changes in flowing bottomhole pressure, flowing behaviour through the tailpipe, separation effectiveness, and changes in production. Challenges were noted, and potential solutions or courses of investigation are proposed. Conclusions were drawn regarding the overall effectiveness of the concept, as well as the relative effectiveness of the two systems. Novel/Additive Information We examined the differences between two tailpipe systems regarding the isolation location, whether at the top or bottom of the tailpipe, to aid us in designing future systems. A comparison of the two separators was attempted, and various operational challenges are discussed so as to improve the design, installation, startup, and operation of these systems.