Vertical Log Research Articles

Shared Earth Models For Multi-disciplinary Teams-A Reality

Three significant areas of advance in horizontal well technology are in drilling, production and reservoir characterization. Both reservoir engineer and geologists are interested in reservoir description for better well placement and flow simulation. It is only through the co-operation of the earth scientists that includes the geologist, geophysicist, petrophysicist, geostatisticians, reservoir simulation engineers, drilling and production engineers etc. that optimized results can be achieved. The current challenge is development of models that propel forward the oil and gas technology by reducing, if not eliminating, the time it takes to react to new inforrilation. Also important is the advance in non-linear geostatistics that allows for risk assessment in horizontal well planning. Why Characterize Reservoirs? Advanced 3D reservoir modelling translates directly into better placements of vertical and horizontal wells. Other benefits of the reservoir characterization are risk reduction, revenue enhancement and better recoveries of the in-place volume. These can be categorized as pre-drill field studies. While-drilling characterization has all the advantages the pre-drill process provides, in addition to cost savings associated with potential reduction of drilling time. Real time reaction to the (ultimately variable) reservoirs has the opportunity to reduce risk and take advantage of additional data. Geologists are most familiar with the concept of variability at every scale of detail. In fact, very few geologists will take a picture of a core or outcrop without a scale such as a hammer or a person because it is nearly impossible to tell the size of the features otherwise. While the complex strata that we see in the form of vertical and horizontal logs, outcrops, cores, seismic x-sections etc., reveal a seemingly chaotic pattern, it can be mathematically shown that within distinct facies the characteristics of data has power law characteristics, otherwise known as fractal properties. Since most current interpolation methods such as kriging are linear and tend to average the results, we tend to lose the variability that is inherent with the data. The measured variability in fractal interpolation is added back into the model and that is why the characteristic of the fractal interpolation is better characterization of flow through solute transport, resulting in smoother history matching. Just as geological interpretations vary for each geologist or geophysicist, new technologies need to honour their interpretation and not to run wild to merely develop a 3D interpretation. Several processes are responsible for the intense interest and advances in 3D or 4D technologies. These include advances and understandings in:Multi-disciplinary co-operation barriers for field development studies are gradually coming down.Geostatistic methods are becoming more acceptable. These dous potential for solving some of the very difficult problems in cementing. The CEA99 project is a fundamental investigation of the inflatables while the objective of the PEA-91 project is to determine operational considerations for improvement of inflatables. Later that same month the CEA-90 project joined with the PEA-91 project to share data. All inflatable manufacturers were asked to submit information on all jobs conducted worldwide between 1994 and 1996.

Quantifying lateral heterogeneities in fluvio‐deltaic sediments using three‐dimensional reflection seismic data: Offshore Gulf of Mexico

Scale‐invariant statistics and strong anisotropy in rock properties are documented from well log and three‐dimensional seismic data in Pleistocene fluvial and deltaic deposits in the Eugene Island 330 field, Gulf of Mexico. Systematic quantification of lateral lithologic heterogeneity within a stratigraphic framework, using reflection seismic data, reveals that fluvial and deltaic depositional systems exhibit statistical behavior related to stratigraphic fabric. Well log and seismic data profiles show a decay in power spectra with wavenumber, k, according to k−β with β between 1 and 2.3. Vertical and horizontal well log data exhibit power law scaling behavior with β between 1 and 2. Horizontal seismic horizon slices were extracted from within fluvial and deltaic deposits. Seismic data from fluvial and deltaic deposits exhibit distinct differences in variance, and each depositional system reveals directional anisotropy in β. One‐dimensional seismic data profiles from the fluvial deposit reveal anisotropy along depositional strike (β=1.1) and dip (β=2.2). The higher correlation observed in the direction of stratigraphic dip for the fluvial deposit may reflect the depositional fabric associated with channel systems. Correlation parameters (β) obtained in specific depositional environments can potentially be used to quantify rock fabric and provide constraints in the modeling of sedimentary processes.

Evaluation of Fractal Models To Describe Reservoir Heterogeneity and Performance

Summary Our work uses fractals to characterize the spatial correlation structures of porosity and permeability of vertical and horizontal logs in a braided-fluvial sandstone reservoir. The data comprise cores and logs of adjacent vertical wells and logs of horizontal wells. Small-scale realizations of interwell heterogeneity were generated with successive random additions (SRA) technique for new observed fractal models. A deterministic description is also developed. Effects of fractal and deterministic reservoir heterogeneity on reservoir performance were studied for waterflood and water-alternating-gas (WAG) injection processes. The effects of scale up on spatial correlation of porosity was investigated. The fractal model of fractional Brownian motion (FBM) in the horizontal direction, having same intermittency exponent as for fractional Gaussian noise (FGN) in the vertical direction, is not supported by log observations in horizontal wells. Fractal character of core and log data of vertical wells is similar. The incremental WAG recovery response compared to waterflooding response is more sensitive to reservoir heterogeneity. Scale-up experiments indicate that spatial correlation structure of reservoir properties may be different at different scales. Results of this paper will be useful for evaluation of infill drilling, and design, selection, and optimization of an EOR process. The proposed techniques also provide a framework to quantify uncertainty in reservoir performance.

Seismic response and construction of seaward dipping wedges of flood basalts: Vøring volcanic margin

Geological and geophysical data from the >900 m of volcanic basement drilled at Ocean Drilling Program Site 642 provide the framework for studying seismic properties of huge extrusive constructions on volcanic margins. The main part of the drilled section, corresponding to a prominent seaward dipping reflector sequence, consists of subaerially emplaced tholeiitic basalt flows and thin interbedded sediments. The basalts exhibit a characteristic velocity and density lava flow distribution reflecting changing porosity, pore aspect ratio distribution and alteration. Stacks of laterally continuous basalt flows appear to have thin‐layer transverse isotropic properties for typical wavelengths in multichannel seismic data. Vertical seismic profiling and average sonic log velocities are similar, 3.77 km/s and 3.88 km/s, respectively, while comparable refraction velocities are 10–20% higher. Synthetic seismogram modeling based on downhole logs shows that basement reflectors originate from interference and tuning effects of numerous basalt flow and interbedded sediment interfaces, though the most continuous reflectors are related to thick flows. Seismic models based on the characteristic velocity and density basalt flow distributions and Site 642 stratigraphy show that reflector truncation and onlap may be caused by seismic interference phenomena in a sequence of landward thinning flows. The base of the dipping reflector sequence, reflector K, correlates with flows in the lower part of upper series basalts, while the transition from basaltic to underlying dacitic/andesitic lavas correlates with a locally defined reflector. A model for the breakup related volcanism includes (1) prebreakup dacitic/andesitic volcanism, (2) early breakup basaltic volcanism infilling the prebreakup relief, (3) main breakup stage with intense, focused volcanism, large subsidence and lava pounding, and (4) late breakup volcanism during a period of decreased subsidence and local off‐axis activity.

Stratigraphic-Structural Interpretation and Reservoir Characterization of Lavaca Bay Field, Calhoun County, Texas

ABSTRACT Lavaca Bay field, located in Calhoun County, Texas, covers approximately 7 mi2 and contains 35 wells that produce from the downdip Greta Carancahua Barrier/Strandplain System of the lower to upper Frio Formation. Since 1964, 19 gas reservoirs have been discovered that have total annual and cumulative productions of 5 and 65 Bcf, respectively; each reservoir is produced by 1 to 3 wells. This paper discusses the detailed stratigraphic-structural interpretation of the Frio section in Lavaca Bay field, specifically emphasizing the three-dimensional architecture of the reservoirs, as well as the flow character within each reservoir. Using the lithofacies interpretation and correlation of 125 well logs of Lavaca Bay and surrounding fields, the Frio Formation (6500 ft thick on average) was divided into nine principal depositional sequences, which were subdivided into component sandstone/shale units. In general, the vertical well log profiles of the depositional sequences show a progradational-aggradational character; the component sandstone/shale units are predominantly transgressive in the lower Frio (sequences I through III) and regressive in the middle-upper Frio (sequences IV through V and VI through IX). The boundary between sequences III and IV provides a well-defined well log signature and is inferred to represent a major sea-level fluctuation. Thickness variation within each unit in sequences I through IV reflects the influence of major growth faulting; however, units of sequences V through IX are only offset by postdepositional displacements of such faulting. Each sandstone/shale unit was characterized by well log and production parameters, including depth to top; total thickness; net-sand thickness (h); relative deflections of spontaneous potential (SP), gamma-ray (GR), and resistivity (R) curves; and initial flow potential. The parameters that were normalized for each well, and some numerical relationships between them, were mapped and compared. Correlative and distinctive trends of thickness, net-sand, and production isolines provided guides for defining individual reservoirs and their structural and fluid boundaries; isoline trends of netsand, SP and GR, and R maps defined internal facies and stratigraphic boundaries of the reservoirs. Extrapolation of these distinctive map trends, supported by the three-dimensional geometry of the sandstone/shale units and their reservoirs, defined prospective intervals and areas for additional hydrocarbon production on each unit. For each unit and its contained reservoirs, the maps of SP and GR relative deflections were considered to represent qualitative values of lithofacies permeability, and therefore (SP)(h) to represent their qualitative values of flow capacity and (SP)(h)(R) to represent their qualitative values of hydrocarbon flow potential; these maps will guide the infilling well program in individual reservoirs. This procedure for characterizing the flow quality of reservoirs from well log parameters is a powerful and practical technique that is validated when core permeability correlates with SP or GR deflection, or both, or (SP)(h) correlates with (K)(h) obtained from transient pressure analysis or with initial production potential. In such cases the qualitative value of well log parameters can be transformed into quantitative values. End_of_Record - Last_Page 561-------

Application of Parasequence Stratigraphy to Reservoir Modeling

The Cretaceous Blackhawk Formation (Masaverde Group), exposed in the Book Cliffs of southeast Utah, comprises a set of progradational, aggradational, and rare retrogradational clastic parasequences dominated by shoreface and sand bodies. Such san bodies form important hydrocarbon reservoirs in the Gulf Cost, the North Sea, and other oil provinces worldwide. The 40-50-m-thick Grassy Member shoreface system comprises three forewardstepping parasequences. Individual parasequences exhibit a systematic distribution of lithofacies and major changes in vertical log profile relative to depositional dip. Parasequence bounding surfaces here are often cemented and/or intensely bioturbated and correlate downdip with a marine flooding surface. each facies association within a parasequence has a characteristic shale distribution which facilitates correlation of internal heterogeneities on well logs. 3-D mapping of individual parasequences provides guidance for sub-surface correlation at common (0.5-1.0 km) well spacings. Shales are divisible into minor flooding surface (feldwide K{sub v} barriers) and several more restricted intra-parasequence types, relating to predominantly autocyclic events. Correct identification of the specific shale types in the vertical sequence uses outcrop dip-log, gamma ray and core analysis (i.e., data obtainable downhole). These results allow more accurate prediction of internal heterogeneity geometries and architecture in shoreface reservoirs and should provide data sets and rulemore » bases for reservoir modeling and simulation.« less

Geologic Applications of an MWD Communications System in a Development Drilling Project, Point Pedernales Unit, California: ABSTRACT

A low-cost communication system for measurement while drilling has been developed. This system has been used effectively on a major development project offshore California. The Point Pedemales unit is currently being developed from platform Irene with Unocal serving as the operator. The user end (remote) of the system is designed to reside on any IBM-compatible personal computer. For the Point Pedernales project, the software was installed on a Unocal system and used the existing microwave voice phone communications. The availability of real-time data in the operator's office results in the elimination of unnecessary trips to the rig site. The flexible plotting capabilities allow true stratigraphic thickness logs to be generated. In high-angle, long-reach wells, these plots allow for more accurate correlation not typically achievable with measured depth and true vertical depth logs. This capability allows for casing point selection to be made accurately. The cost savings associated with accurate casing point selection can be significant. The ability to transmit MWD data from the drilling rig to the office allows all personnel involved in a project to take advantage of the real-time benefits of MWD. The systems lends itself to installation on any drilling Project where voice phone communications, including cellularmore » networks, are available.« less

Poker Flat MST radar observations of shear‐induced turbulence

Wind speed and Cn2 measurements made with the Poker Flat, Alaska, MST radar are used to study the development of clear air turbulence (CAT) near the tropopause. Arguments and observations indicating that Cn2 is proportional to the intensity of turbulence are presented. The relationship between wind shear and turbulence is examined by using time‐lagged cross correlations between vertical wind shear and log Cn2 time series. From analysis of data taken with spatial resolutions of 2200 m and 750 m, it is found that the correlation improves as the time and spatial resolutions of the measurements improve. The implications for forecasting CAT are discussed, based on the correlation results and a comparison of radar data with National Weather Service CAT forecasts.

Notes on Flight and Host-Selection Behavior of the Pine Engraver,Ips pini(Coleoptera: Scolytidae)

In the presence of attractants, Ips pini (Say) flew upwind, but upwind response decreased in winds above 1 mile per hour. Beetles tended to fly downwind in the absence of attractants. Released insects flew higher at lower wind velocities and higher temperatures; their maximum flight speed was 3–4 mph. Beetles exhibited host material preferences by selecting Pinus resinosa over P. strobus logs, and by selecting horizontal over vertical logs.

On variations in the current at the Seven Stones Light Vessel

Measurements of current at the Seven Stones Light Vessel, 50° 03·5' N. lat., 6° 05·1' W. long. (for position, see Cooper, 1960b, fig. 1) were first made with the Carruthers Drift Indicator between 17 August and 15 September 1933 (Carruthers, 1934). The much longer series with the Vertical Log between July 1939 and April 1941 showed average travel of the residual cur-rent at a rate of 2·5 miles per day towards east-south-east (110° true) (Carruthers, Lawford & Veley, 1951). It was shown clearly that there was a strong causal connexion between the direction and strength of the wind and direction and strength of current, but that there were evidently other factors concerned as well. These current measurements were not easy to reconcile with deductions from the observed distributions of temperature and salinity in the area (Matthews, 1914; Harvey, 1925, 1929; Cooper, 19606). A rational explanation could be achieved if it is assumed that the passage of water from the English Channel to the Bristol Channel occurs intermittently and is confined to a narrow current close into Lands End. This ‘corner current’ rarely extends as far west as the Seven Stones Light Vessel.

The Theory and Practical Application of Vertical Log Frame-Saws

Wood is one of the most important of raw materials; it can be used in various ways to meet demand, and can also be grown as required. In spite of its extensive use throughout the ages, and the wastage caused by fire and axe, there still exist huge virgin forests, covering partly unexplored regions of the world, whilst scientific forest management gains increased scope in keeping the timber resources in line with the constantly growing demand. Saw-milling is one of the main methods employed in wood conversion, producing sawn timber such as boards, planks, battens, and cants. Three types of saw-mill head rigs are used, i.e. circular, band, and frame. This paper deals with certain particulars related to the reciprocating type—the frame- or gang-saw. The circular- and band-saw-mills use continuously moving saw-blades, but frame-saws have to be sufficiently powered and strong enough to take up the great force developed by the reciprocating motion of the saw-gate, blades, and all accessories. The first patents and other technical literature relating to almost any type of woodworking and saw-mill machinery are of British origin. At the beginning of the Industrial Revolution Britain was leading for many years in the manufacture of these machines, but more recently frame-saws and other types were developed in many parts of the world, where a growing saw-mill industry has had to satisfy its needs for such machines, well suited to local demands. It should be a matter of topical interest to give some details here of the close relationship between theory and practice in their application to the frame-saws, due to the fact that enormous damage was done during the recent war years, not only to all kinds of property which requires urgent replacement, but also to the fact that numerous saw-mills have first to be put in order, before they can again produce the timber needed for urgent repair work.

The heliochromoscope

Insects that rely upon aggressive bark beetles (Coleoptera: Scolytidae) for generating appropriate habitats (natural enemies and associated species) must respond to a variety of stimuli used by bark beetles, including semiochemical and visual cues. In the southeastern US, Ips engraver beetles are non-aggressive bark beetles that exploit both standing and downed trees (vertically and horizontally oriented targets). The objective of this experiment was to evaluate whether changes in visual silhouettes (color and orientation) affected the colonization patterns of Ips engravers and their natural predators in loblolly pine logs. We found that the total number of Ips arriving at loblolly pine logs was significantly affected by color. About 48% fewer Ips were caught at logs painted white than those painted black, and 32% fewer than at unpainted. Of the predators arriving in sufficient numbers to evaluate, Medetera bistriata parent (Diptera: Dolichopodidae) and Platysoma spp. (Coleoptera: Histeridae) were significantly affected by color, with white logs catching fewer numbers in each case. Orientation of host logs (horizontal and vertical) affected both M. bistriata and Lonchea spp. (Diptera: Lonchaeidae) but not Ips. Lonchea were significantly and consistently more attracted to horizontal logs. M. bistriata, on the other hand, were inconsistently more attracted to vertical logs, i.e., the interaction between season and orientation was as strong as the main effect for orientation. Thanasimus dubius (F) (Coleoptera: Cleridae) and anthocorid bugs were not caught in sufficient numbers for valid analysis. Overall, these results are similar to those obtained by funnel trapping, suggesting that visual responses are robust across different environmental conditions. Further, our results suggest that color treatments could be used to manipulate behaviors of predators and prey somewhat independently. This may be important for research, to evaluate relationships at a range of densities, and management, to develop treatments that reduce losses of natural enemies when bark beetles are targeted.