The rebirth of the Leduc-Woodbend Nisku oil pool in Alberta, Canada

Statistical analyses of size, orientation, and pressure measurements on Cretaceous and Jurassic oil and gas pools in Albeta reveal general predictable trends and some significant anomalies. The total oil and gas in place, and the plan areas of pools, appear to be lognormally distributed although this cannot be proved statistically. For major reservoirs showing a well-defined lognormal size-frequency distribution, the probability of future economic exploration success in that unit can be evaluated from the general trend. Notable deviations from the lognormal distribution pattern occur for Viking oil pools and Wabiskaw (Glauconitic) gas pools. The presence of two populations of pools (one of large pools and one of small pools) can explain the anomalous size-frequency distribution. The large, and therefore more profitable, oil pools in the Viking Formation occur in the Main Viking sand in areas of favourable hydrodynamics. For the gas pools in the Wabiskaw, a factor analysis indicates a relationship between the size of the pool and a combination of porosity and elevation of the reservoir. A map of factor loadings defines an area on the southwestern edge of the basin in which the large Wabiskaw pools are more likely to be found. For oil occurrences in Viking, Cardium, and Belly River reservoirs, the size of the pool can be predicted reliably from its plan area. Consequently, for these reservoirs the reserves potential of an exploration target can be estimated from the untested area. Gas reserves are generally less predictable from plan area. Diagrams showing the orientation of oil and gas accumulations in major reservoirs have both analytical and predictive applications. The orientations are caused by the original depositional conditions, and by later structural and hydrodynamic effects, and are used to identify the controlling features. A quantitative knowledge of the orientation directions of oil or gas pools in a particular reservoir will influence the extension of a new oil or gas discovery in that reservoir. Plots of pressure against depth for oil and gas pools reveal that the interconnected reservoir systems such as Gething Formation and Ellerslie (Basal Quartz) Member have well-defined pressure gradients close to hydrostatic. Groupings of pools on the Ellerslie Member plots, when mapped, define a western limit for the occurrence of oil in the Ellerslie. Maps showing the areal occurrence of oil and gas in Cretaceous and Jurassic reservoirs in Alberta delineate hydrocarbon-rich belts trending NW-SE. Some well-explored areas of the province have very small quantities of oil and gas discovered, apparently for lack of suitable reservoir units.

Canada has played a prominent role in the development of horizontal drilling technology. To date, over 1,400 "grassroots" and "re-entry" wells have been drilled. Although other countries have experienced greater numbers of wells, the number of different types, varieties, and formations tested with this technology in Canada is unparalleled. Due in part to the exponential growth of horizontal well applications since the mid-1980's, coiled tubing CCT) technology in Canada has been adapted and evolved for more traditional uses such as horizontal well stimulation, evaluation, workovers, and clean-outs. The principal nontraditional aspect of CT is its use in drilling operations. This paper will deal with the current state and recent advances in CT horizontal drilling in Canada, A brief historical perspective will be presented that highlights Canada's presence as a pioneer in CT drilling and documents its evolution from vertical re-entries dating back to 1974, grassroots vertical wells in 1976, to the industry's current efforts at vertical and horizontal CTD. The principal Canadian service companies are reviewed in terms of present capabilities in CTO applications and the perceived driving forces that are stimulating the development of this emerging technology. The key factors such as diameter and fatigue life of the coil, length limitations, bottom hole assemblies, surveying methods and the economic and market factors affecting CTO relative to more conventional drilling techniques are reviewed. Finally, the future technological, market and economic developments necessary for the successful implementation of CTO for grassroots vertical and horizontal well re-entry projects are suggested. Introduction The exponential growth in the number of horizontal well applications in Canada and internationally over the past eight years has led to a relatively rapid development of both personnel and equipment to enhance the horizontal drilling method of exploiting existing oil and gas pools. In Canada, there are an estimated 70,000 producing wells: 40,000 gas wells and 30,000 oil wells. Recently, the National Energy Board (NEB) presented a study on horizontal oil wells and their impact on future crude oil supply in Canada. They estimated that there is a potential market of over 12,000 horizontal wells that can be economically drilled within 1,800 oil pools at a market price of $20 US/Bbl. Of these 12,000 wells, 5,000 were believed to be grassroots in nature (1 I 100 have been drilled to date) while 7,000 were horizontal re-entries through existing cased wells (300 have been drilled to date). Of the 6,700 remaining re-entries, the competition for services will be between slim hole (less than or equal to 6–1/4 in. hole size) conventional drilling systems using drilling rigs or modified service rigs and coiled tubing drilling (CTD) technology. Add to this potential market vertical deepenings, horizontal lengthenings and grassroots wells coupled with increasing interest in horizontal exploitation of gas pools, and the development of CTD appears to be poised for exponential growth in Canada over the next five years. Some of the questions that will be addressed during the course of this paper are:

The commercial oil and gas pools are on crests of closed anticlines and domes except in the General Petroleum field, where oil is found in variable shaly sandstone beds on a pitching anticline without structural closure. The oil sand of the G. P. field (G. P. sand) is not productive elsewhere even on closed structures. Commercial oil is found in the Mowry shale on the crests of the three sharpest folds-Little Lost Soldier, Wertz, and Ferris. It is not found in the Mowry shale on the gentler folds or elsewhere. Seemingly the maximum fracturing and other mechanical effects peculiar to the crests of sharp flexures are necessary to the formation of the shale oil pools or pockets. The productivity of the structures, other factors being equal, is in close relation to the extent to which they are fractured and faulted. Burial of the productive sand beneath a great thickness of shale is equivalent to diminution in faulting, since the faults may be sealed or may not persist to great depths. The more numerous and open the faults, the greater the tendency toward an oil pool or to barrenness through more or less complete leakage. The fewer and tighter the faults, the greater the tendency toward a gas pool or to barrenness through lack of migration and accumulation. With the Lost Soldier and many other oil and gas fields of the Rocky Mountain region as confirmatory evidence, it may be said that, in the post-Paleozoic strata of the region (i) water in an upper sand is not indicative of what is to be expected in lower sands, whether oil, water, or gas; (2) gas, as the predominant product in an upper sand, means that lower sands may be expected to be primarily gas sands; and (3) oil, as the predominant product in an upper sand, indicates that lower sands are likely to be primarily oil sands.13J. S. Irwin, “Faulting in the Rocky Mountain Region,” Bulletin Amer. Assoc. Petrol. Geol, Vol. 10 (1926), pp. 127-28.

Source controls on geochemical characteristics of crude oils from the Qionghai Uplift in the western Pearl River Mouth Basin, offshore South China Sea

Conditions for the formation of oil and gas pools in Tertiary volcanics in the western part of the Huimin sag, Shandong and their distribution have been studied based on the geological, seismic and well‐logging information. In this paper, the types and lithofacies of the volcanic rocks in the western part of the Huimin sag are described; the relationship between rocks and electrical properties, the seismic reflection structures, the development and distribution of the volcanic rocks are expounded; and the fourfold role of the volcanic activities in the formation of the oil and gas pools is also dealt with. It is considered by the authors that the volcanic activities were not destructive to the formation of oil and gas pools but a factor favourable to the accumulation of organic matters and their conversion to hydrocarbon. The volcanic rocks might have served as reservoir rocks and cap rocks, or as a synsedimentary anticline. The prerequisites and important factors for the formation of oil and gas pools and their distribution are pointed out in the paper.

Summary This comprehensive study of the geological characteristics of a carbonate oil pool involves multiwell testing, interference testing, and pulse testing. From the calculation and analysis of 32 well-testing curves, sketches are drawn showing the distribution of various parameters of the whole area. On the basis of the parameters of the whole area. On the basis of the permeability (k) distribution chart, the anisotropic permeability (k) distribution chart, the anisotropic heterogeneity of permeability and its distributional pattern are analyzed. Pulse testing data are presented and pattern are analyzed. Pulse testing data are presented and compared with those of interference testing. A rough distributional chart for permeability is proposed for use in numerical simulation. Introduction Multiwell transient testing includes interference testing and recently developed pulse testing. Kamal has given an introduction to the combined use of the different well test methods in the study of formations and Earlougher has reviewed the techniques of interpretation of various parameters. parameters. The type-curve matching method is generally used in the analysis of interference testing data. Type-curve matching, as a characteristic line method with its high accuracy, may eliminate the errors from the use of different characteristic-point methods, caused by the irregular distribution of points actually measured. Pulse testing is a new form of multiwell testing recently developed by Johnston et al. With the use of pressure transients of the initial stage, the method gives results similar to those of interference testing but in a shorter duration than the latter, so that the influence of pressure trend of the oil pool may be avoided. Pierce and Kamal have proposed several charts for interpretation of parameters from the curves. Kamal's chart is particularly useful for unequal pulse and shut-in periods, particularly useful for unequal pulse and shut-in periods, simple and practical for both pulse-test design and data interpretation. Applications of multiwell testing in the study of oil fields are many. Matthies' application of interference tests in the Wolfcamp field, McKinley et al.'s detailed reservoir description of an oil field by pulse testing, and Pierce's study of the distribution of faults in the Kelsey Pierce's study of the distribution of faults in the Kelsey field are among the most illustrative. Ramey's analysis of well pairs in a nine-spot pattern for a homogeneous anisotropic system deserves particular mention. He provides a complete set of data for an oil province provides a complete set of data for an oil province valuable for the interpretation of its anisotropic characteristics and useful for further study of the province. There are plenty of instances describing the province. There are plenty of instances describing the techniques of study--e.g., Ramey et al.'s study on the effect of faults and Vela et al.'s study on reservoir heterogeneity. However, as Kamal pointed out, while there are some ways to interpret data pertaining to homogeneous anisotropic or isotropic formations and to multiwell testing of different kinds of bounded systems, none is available for the heterogeneous formations. The only solution is to try numerical simulations of hypothetical models. In interference or pulse testing at the oil field, a highly sensitive pressure gauge is the most important tool. The measuring system of Johnson and Raynor rendered useful service in the pulse tests. The recently developed quartz pressure gauge is also an efficient instrument for pulse testing, The CY-733 differential pressure gauge for multiwell testing enables us to gather a considerable amount of relevant data. This bottomhole instrument uses a glass piston-cylinder as the pressure-sensitive element, with piston-cylinder as the pressure-sensitive element, with sensitivity of about 0.14 psi [0.97 kpa] in wells 6,560 ft [2000 m] deep and 0.014 psi [0.97 kpa] in shallow wells 660 ft [200 m] deep. The instrument can work continuously for more than 10 days in one run. It is simple in structure and suitable for measuring small pressure variations at specific spots. This paper presents a case of a limestone oil pool that is trapped by a faulted and weathered surface. It describes the multiwell testing program, shows the distribution of reservoir parameters, and gives essential data obtained from interference and pulse testing, interpreted according to the method recommended in the literature. Principles and Methods Principles and Methods What is Multiwell Testing? The multiwell testing technique is a method of studying the formation by observation of the transmission of pressure transients in an elastic system (i.e., a reservoir). A well pair is used as the unit of interference testing (see Fig. 1). Pulse testing and interference testing are analogous in method, and both use well pairs as the units of testing. JPT

Summary The paper puts forward the calculation of the change in time of the minimum downhole pressure of flowing due to the joint interaction of the well and the oil pool under the dissolved gas regime, as well as the method of calculating the conditions of joint operation of the oil pool and the folowing well. The method is based on solving the equations of fluid filtration in the oil pool and the movement of gas-oil flow in the wellbore.

A technique for using two lasers operating in tandem to remotely ignite oil pools in the harsh Arctic environment has been developed. A CW CO2 laser preheats a localized area of the oil pool for several seconds, thereby raising the surface temperature above the fire-point. A fire is then ignited by a focused high-power pulse from a second laser. The fire sustains itself and spreads when the absorbed laser energy is distributed, by convection in a thin surface layer, over a sufficiently large area. An optical system has been designed which allows the laser beams to be focused and directed onto oil pools from a helicopter.

Oil and gas pools: the fundamentals of formation, prospecting, and exploitation

Evolution of a basin implies interaction of two general processes: the process of crust collapse with regeneration of geosyncline belts, and the process of cratonization of the crust. The process of geosyncline belt regeneration with partial displacement across the area occurred three times in western Siberia. The first displacement is dated as long as 1.6 Ga, the second one took place at 650 Ma, and the third at 500 Ma. There were three cratonizations of the first rank: 680 Ma, 520 Ma, and 250 Ma. The last, Hercynian, cratonization has been more intensive in the southern part of the region and has resulted in Triassic-Middle Jurassic taphrogenesis on the background of arched uplifts. Organic-matter transformation and formation of oil and gas pools repeated in the Paleozoic and Mesozoic. In the Cenozoic, the formation of oil and gas pools took place only locally. The process intensity varied depending on the basin geodynamics and geothermal regime. This caused a considerable range of oil and gas interval and resources in different regions. The distribution of hydrocarbon pools is of regular character only in separate oil- and gas-bearing complexes, except the secondary pools which are confined to Paleozoic basement weathered rocks occurring in allmore » areas of the petroliferous basin. The largest hydrocarbon pools of Lower Jurassic deposits are more common in the western regions, and pools of Upper Jurassic deposits occur in the eastern ones.« less

At the first stage of seismic action, the attenuation of acoustic waves in real (porous, creviced) rocks is always related to the energy pumping to high-frequency (ultrasonic) modes, and only at the next stage are these waves converted into chaotic thermal oscillations, so that the entire phenomenon refers to a basic problem of nonlinear seismics. Several physical phenomena related to the excitation of ultrasound and the corresponding transformations of the wave spectrum (including the dry friction in contacts, the instability of viscoelastic oscillations, the seismic energy pumping to the rotational modes, and the resonance of gas bubbles in natural oil) are considered in relation to the development of vibroseismic methods of acting upon a producing oil pool. The results of experiments on the ultrasound-stimulated water displacement of natural (gas-saturated) oil from a porous medium are presented, in which the oil recovery reached up to 90%.

The Tarim Basin is the largest inland basin in China. The hydrocarbon charge history of the Silurian bituminous sandstone reservoirs in the Tazhong uplift was investigated using an integrated approach, combining detailed petrographic analysis (thin section, scanning electron microscopy, and transmission electron microscopy), clay mineral x-ray diffraction characterization, and modeling of authigenic clay minerals and subsequent potassium-argon (K-Ar) dating of authigenic illite. The timing of the hydrocarbon charges of the reservoirs in the Tazhong uplift area is compared with that of the Kongquehe area within the basin. The authigenic illite ages in the Tazhong uplift area and the Kongquehe area range from 383 Ma to 204 Ma, indicating a unique age distribution pattern in the basin. The Silurian oil accumulations were primarily formed in the late Caledonian through the late Hercynian. The reservoirs within wells Qiao-1, Kongque-1, Longkou-1, and Yingnan-2, located in the western area and the eastern area of the basin, were charged around 383 to 271 Ma in the late Caledonian to the early Hercynian. The reservoirs in wells Tazhong-37, Tazhong-67, Tazhong-12, and Tazhong-32, located in the center of the basin, were charged at around 235 to 204 Ma in the late Hercynian. A correlation between the authigenic illite ages and the thickness of the Silurian bituminous sandstones suggests that the paleostructural framework is a key controlling factor. The paleo-oil pool located in and around the sedimentary centers, such as wells Qiao-1 and Kongque-1, was formed relatively early (383 Ma). The K-Ar dating results were consistent with the results of conventional hydrocarbon accumulation history analysis and highlight the differences in the accumulation timing between various oil pools in different parts of the basin.

Flame expansion behavior induced by a water droplet impacting on burning and stratified oil-water pool

The reservoir is composed of a mixture of dolomite, limestone, anhydrite and shale interstratified with sandstones member. The sandstone is predominantly poorly consolidated and quartz rich. Much of the sand is medium grained although coarser sand is common in the lowermost thick sandstone units. Both anhydrite and carbonate cements are present within the sandstone with the anhydrite dominating in the uppermost units. The basal sand syones are often shaly and silty. The sandstone porosity value range from 9% to 26% with typical values being from 22% to 24% substantially better than the interbedded carbonate units with typical value of 12% to 15%. Permeabilities over 2 Darcies have been measured in this field. The carbonate can have higher permeability, calculated1 from flow tests, as a result of fractures within the carbonate. Borehole imaging provided is a new way of the characteristics of reservoirs drilled with oil-base-mud. Complicated structures were resolved utilizing the dip data gathered with such techniques. Fractures were characterized for their aperture (open or closed), intensity of fracturing, and directional attributes. In addition to structural details, the Oil base mud imaging provided quantitative resistivity of invaded zone measurement in oil-base-mud environment. It helped to understand invasion profiles, which generally is a function of permeability, in carbonate and sandstone reservoirs and helped reservoir engineers and petrophysicists to understand response of reservoir formation tester measurements for formation pressure and reservoir fluid mobility. Introduction The structural style of the fields in this area is complex. Precise information on the structural dip and fault pattern in the subsurface is mandatory to plan development / infill wells successfully. The areas that appear to have low dips turn out to have steep dips, hence cause the wells to miss the targeted reservoirs or oil column even if they have penetrated the reservoir. To get to the reservoir, such wells have to be sidetracked in the right direction so that the missed reservoir or oil pool could be penetrated. Geologists assess vertical and lateral changes in the reservoir by identifying and characterizing large-scale depositional events and sequence stratigraphic boundaries across fields. Using borehole-image data, they also define and determine the orientation of smaller depositional features to understand stratigraphically controlled reservoirs. Dip Analysis done using manually computed orientations of geological features from the images provide the attitude of the structural and the depositional framework. In the present study, logged intervals of studied well present a medium dipping sequence with dip azimuth towards Southwest. Fracture analysis is one of the most important objectives of borehole imaging in the study well. Borehole images were used to identify open and closed fractures. Sand Count analysis performed using the high-resolution azimuthal data from the borehole image was successful in identifying the thin sand beds, which are generally overlooked by the conventional logs. The method is capable to provide a more accurate estimate of net reserves. Facies or rock type classification, using the artificial neural net technique was successful in replicating rock classification. An average quantitative resistivity of invaded zone was derived by laterally averaging all 20 resitivity curves from borehole2 image log. Separation borehole image resistivity curve from the Induction curves, caused by invasion of the formations with the oil base mud. Generally the zones with larger invasion have higher mobility and those with minor invasion have lower mobility. In some cases however the average quantitative resistivity of invaded zone may provide at least an indication of the fluid type, ie the water saturation.

Exploratory drilling in the shallow-sand territory of western Pennsylvania (Upper Devonian or higher) during 1949 led to the discovery of 3 new gas fields. One of these may be proved significant in size. No new oil pools were discovered. The total number of shallow wells drilled, exclusive of those drilled in connection with underground gas storage and secondary-recovery oil operations, was 17 per cent less than in 1948. In the Pennsylvania part of the Bradford oil field, which continued to be the most active area, 1,100 new wells were completed, as compared with 2,070 in 1948. About half of these were water-intake wells. The Bradford field accounted for 79 per cent of the total oil production in Pennsylvania during 1949. The average daily oil production in the state in 1 49 was 31,347 barrels, as compared with 35,206 barrels in 1948. Twenty-seven new wells were completed to the deeper formations (Onondaga or deeper) as compared with 30 in 1948. Of these, one was drilled for gas storage purposes. Of the remainder, 16 were gas wells and 10 were dry holes. One may lead to the development of a new Onondaga chert gas field. The greatest activity centered in the East Fork-Wharton Oriskany sand gas pool of north-central Pennsylvania where 13 wells were completed, whose initial open-flow capacities ranged from 165 thousand to 22 million cubic feet per day. The W. R. Barton Estate well No. 8 in the South Summit field of Fayette County, drilled to the depth total of 10,312 feet, is now the deepest in Pennsylvania and the Appalachian province, and also has the distinction of being the deepest well in the world to be drilled ntirely with cable tools. A significant discovery in the Oriskany sandstone was made in Leidy Township, Clinton County, in north-central Pennsylvania shortly after the close of the year. A wildcat well on the Wellsboro anticline, 10 miles southeast of the East Fork-Wharton pool, encountered gas under a reservoir pressure of 4,200 pounds per square inch. The initial open-flow was estimated at 10-15 million cubic feet per day. The discovery has focused attention on a large area that has not yet been explored.