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Collaborating Authors
Louisiana State University
Formation Evaluation Using In Situ Measurements Of Formation Thermal Properties
Xu, Hui (Louisiana State University) | Desbrandes, Robert (Louisiana State University)
ABSTRACT This paper presents a formation evaluation method that uses the thermal properties (volumetric heat capacity and heat conductivity) of geological formations determined from in situ temperature measurements. The methods used to determine formation thermal properties are similar to the methods used in well pressure testing. A temperature logging tool located at the depth of interest in an open hole or a cased well continuously records the temperature during a cold fluid circulation, when a temperature drawdown is recorded, and after the circulation when a temperature buildup is recorded. The formation thermal properties can be obtained by analyzing the temperature buildup curve using methods similar to those used in well pressure testing analysis. A crossplot using the formation volumetric heat capacity and heat conductivity was developed for formation evaluation. This crossplot is based on the equation of porous rock volumetric heat capacity and an improved equation of porous rock heat conductivity. By entering the crossplot with the formation volumetric heat capacity and heat conductivity, the formation porosity and hydrocarbon saturation can be found. Heat conductivities measured in some rock samples were used to verify the improved heat conductivity equation. The calculated rock porosities and hydrocarbon saturations agree with the measured values. The temperature drawdown and buildup measurements were taken at four intervals in an LSU test well. The formation thermal properties were computed with the temperature recordings. The formation porosities and gas saturations were calculated from the thermal properties. The calculation results agree with the interpretation analysis of the pulsed neutron log recorded previously. Temperature logging, one of the cheapest logging methods, can be applied to conventional open hole formation evaluation or to old well interpretation to find overlooked hydrocarbon zones. It can also be used in thermal recovery where the formation thermal properties can be found by using the crossplot when the formation porosity and hydrocarbon saturation are known.
- Reservoir Description and Dynamics > Formation Evaluation & Management > Well performance, inflow performance (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Drillstem/well testing (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
Transient Pressure Analysis in Partially-Penetrating Wells
Yildiz, Turhan (Louisiana State University) | Bassiouni, Zaki (Louisiana State University)
Abstract A new mathematical model is developed to predict the transient pressure behavior of a partially-penetrating well PPW). The model is derived by solving the two-dimensional (2-D) diffusivity equation. The Laplace transformation and the separation of variables technique are used. A convolution technique is used to incorporate the wellbore storage and skin factor. The solution has the form of the infinite Fourier-Bessel series and can be easily implemented using a personal computer. Using the new model, the pressure behavior of a PPW is analyzed, and the approach of current interpretation techniques is investigated. Currently, it is claimed that a plot of pressure versus log (time) displays an early- and a late-time straight time. It has also been assumed that there is a spherical flow period between the early-time and late-time radial flow regimes. This investigation shows that there is neither early-time straight line nor spherical flow period. What may appear to be a straight line on these plots is merely the result of an inflection point. Therefore, the interpretation techniques based on the existence of an early-time radial flow period and spherical flow in the transition period are questionable. Further study has also shown that the type-curve matching methods provide a non-unique solution. Pressure-derivative and pressure-integral behavior of a PPW are also examined. Derivative and integral type curves were constructed, and their ability to interpret the test data is investigated. A new interpretation technique is proposed to alleviate the short-comings of existing methods. The new method provides unique solutions to horizontal and vertical permeability's and skin effect. The method is based on the de-convolution of measured pressure and flow rate data. The limitations of the proposed interpretation technique are also outlined. Introduction Often, only a portion of hydrocarbon-bearing formations is perforated. Occasionally the borehole does not completely penetrate the entire formation. Such well completions are referred to as restricted-entry, limited-entry, or partially penetrating wells. The transient flow behavior of a PPW is different from that of a fully penetrating well (FPW), as illustrated by Fig. 1. In the case of a FPW, adequately described by one-dimensional radial flow, a plot of pressure versus logarithm of time yields a straight line whose slope is related to formation capacity. Transient pressure response is more complex in the case of a PPW. Transient pressure response of a PPW has been extensively studied. Several models were derived by solving the two-dimensional (2-D) diffusivity equation with various mathematical techniques. Among the mathematical methods used are Greens' function, integral transformations, and finite differences. In most studies, the final solution is not in closed form and requires long computation time. Usually, wellbore storage and skin factor were not included in the models. Most of the studies present equations either to predict the pressure response of a PPW to fluid withdrawal or to determine the pseudo skin factor for a given set of reservoir data. Interpretation of measured pressure data to determine reservoir parameters such as permeability and skin factor due to damage has been attempted only in a few studies.
Organic Geochemistry of Sediments of Deep Gulf of Mexico Basin
Fang, J. (BP Exploration) | Sassen, R. (BP Exploration) | Chinn, E.W. (Louisiana State University)
ABSTRACT Rock-Eval pyrolysis of 687 core samples from the Mississippi submarine fan and Orca and Pigmy Basins in northern Gulf of Mexico has revealed that TOC and hydrogen index are, respectively, 0.82% and 103 mg HC/g TOC. Tmax values average 425° C. It is concluded that the sediments of Pleistocene and Holocene age in the deep Gulf of Mexico Basin are organic-lean, thermally immature, and are not obvious analogs to the source environments in the geologic past that gave rise to Gulf Coast crude oil. INTROPUCTION Despite the immense volumes of hydrocarbon production from the Gulf Coast Tertiary, especially from the Miocene and younger reservoirs, the origin of crude oils has not been thoroughly documented. study on the origin of the crude oils in the northern Gulf of Mexico has been the subject of many efforts in recent years. It was believed that oil and gas were generated and expelled from shallow water shales "soon after deposition and burial" . Clark and Rousesuggested that all environment, structural, and stratigraphy elements necessary the generation and entrapment of hydrocarbons were present within the Cenozoic deltas of the Louisiana Gulf Coast and constitute a closed system which is responsible for the large hydrocarbon accumulations in the Cenozoic oil fields of the Louisiana Gulf Coast. These ideas were based on geological grounds and absent of research on source rock potential and thermal maturity. Many organic geochemists accept that crude oil andthermogenic gas in reservoirs of the GUlf Coast Salt Basins are the result of vertical migration from deep source rocks . Nunn and sassen suggested that the generation of crude oil and thermogenic gas take place at great depth in sediments of the Gulf Coast Basin. The enormous accumulation of hydrocarbons in the basin resulted from vertical migration from deeply buried Mesozoic source rocks that are not usually encountered by drilling. The purpose of the present study' is (1). to determine kerogen type, abundance and thermal maturity of organic matter in samples coring at DSDP (Deep Sea Drilling Project) Leg 96 from site 614A through 624, (2) to assess the generative potential for crude oil of the sediments, given deeper burial and higher levels of thermal maturity. The study area is located in the Gulf of Mexico Basin (Fig. 1). Cores from nine DSDP Leg 96 Mississippi Fan sites and two intraslope basin sites provided samples for pyrolysis analysis. Samples come from middle fan sites 617, 620, 621 and 622, lower fan sites 614, 615, 623 and 624, and the two intraslope basin sites (Sites 618 and 619) (Table 1). The present study is based on the pyrolysis results of the 687 samples from these cores. SAMPLES AND METHOPS Sediment samples were collected on the Glomar Challenger during DSDP Leg 96 . The cores used in this study were taken in water depths of 2495 to 3314 m, and from the youngest fan lobe and the two intraslope basins (Fig. 1), of Pleistocene age, in the Gulf of Mexico Basin. Amount cored varied considerably, ranging from 75 m to 421.3 m (Table 1).
- North America > United States > Gulf of Mexico (0.70)
- North America > United States > Mississippi (0.55)
- North America > United States > Louisiana (0.45)
- North America > United States > Mississippi > Mississippi Salt Basin (0.99)
- North America > United States > Gulf of Mexico > Gulf Coast Basin (0.99)
- North America > United States > Gulf of Mexico > East Gulf Coast Tertiary Basin > Pigmy Basin (0.94)
- North America > United States > Gulf of Mexico > East Gulf Coast Tertiary Basin > Orca Basin (0.94)
In fluid flow systems where there are no waters originally deposited with these strata.
- Geology > Sedimentary Basin (0.53)
- Geology > Geological Subdiscipline > Geochemistry (0.48)
Oil Detection In Fractured Carbonates Of Chapayal Basin, Guatemala
Bassiouni, Zaki (Louisiana State University) | Lau, Milton N. (Louisiana State University)
Quantitative determination of fluid saturation in naturally fractured reservoirs has proven difficult. Conventional quantitative well log evaluation techniques cannot be applied successfully because of the complex nature of fractured formations. Well logs have, hence, been used almost exclusively for qualitative fracture detection. This paper presents a quantitative evaluation technique that makes use of the Pickett crossplot to identify oil-bearing formations. This method does not emphasize fracture detection; instead, it attempts to directly compute the "total oil saturation" in the zones of interest. The parameter "total saturation" is an oil saturation index combining the effect of both the intergranular pore system and fractures. Furthermore, this study introduces a new method used to correct the Neutron Log readings for borehole effects induced by fractures. The proposed quantitative interpretation method was successfully applied in several naturally fractured intervals of 23 wells drilled in the Chapayal basin of Guatemala. The evaluation of three typical wells is included.
- Oceania > Australia (1.00)
- North America > United States > Oklahoma (1.00)
- North America > United States > New Mexico (1.00)
- (17 more...)
- Geology > Rock Type > Sedimentary Rock (0.67)
- Geology > Mineral (0.67)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > United States Government (0.92)
- Asia > China > Tianjin > Bohai Basin > Huanghua Basin > Dagang Field (0.99)
- North America > Canada > Alberta > Western Canada Sedimentary Basin > Alberta Basin > Calgary Field (0.98)
- North America > Canada > Alberta > Lane Field > Barr Lane 5-32-65-7 Well (0.98)
- Europe > United Kingdom > North Sea > Central North Sea > Kittiwake Area > Block 21/18 > Fulmar Formation > Eagle Well (0.98)
A New Model To Determine Permeability From Wireline Formation Testing
Yildiz, Turban (Louisiana State University) | Desbrandes, Robert (Louisiana State University)
ABSTRACT Wireline formation testing (WFT) is an open-hole logging technique used to measure vertical pressure distribution and formation permeability. In the present analysis of the WFT test data, the flow geometry is oversimplified. Also, the drawdown and build-up portions of the test data are evaluated separately. The drawdown data is analyzed by using the steady state spherical flow with a correction factor for simplifying the flow geometry. Since there are two drawdown periods, this gives different drawdown permeabilities (kd1 and kd2). If the drawdown periods do not reach the steady state, then an integration scheme on the WFT test data is used to determine the formation permeability (kdint). The buildup portion of the test is analyzed by means of transient flow models. A radial or a spherical flow configuration is assumed. The use of transient spherical and radial flow models gives another permeability value, spherical or radial permeability (kbs or kbr). Therefore, four different permeabilities are deduced from only one set of WFT test data which often differ significantly. Also radial and vertical permeabilities cannot be determined from the spherical permeability. In the first part of this study, a new model was developed to simulate the exact flow geometry of the WFT test assuming a constant drawdown rate. The model was derived by solving the 3-D diffusivity equation coupled with prevailing boundary conditions. The Laplace transformation and the separation of variables technique were used in the solution. The solution is expressed interms of the infinite Fourier-Bessel series in the Laplace space and inverted into the real space by means of the numerical Stefhest algorithm. Small-time and large-time solutions were also obtained for faster numerical convergence. In the second part of this study, the model was extended to cover both the drawdown and the buildup period by means of the superposition theorem. This enables us to analyze all the WFT data using only one single model. The model was used to construct type curves for easier use. Therefore, the analysis is simply to match the real WFT data with one of the type curves generated by using the model.
- North America > United States > Louisiana (0.28)
- Asia > Middle East > Turkey (0.28)
Carbonate Buildups on the Continental Slope Off Central Louisiana
Roberts, H.H. (Louisiana State University) | Sassen, R. (Louisiana State University) | Carney, R. (Louisiana State University) | Aharon, P. (Louisiana State University)
ABSTRACT Hydrocarbon exploration and production on the Louisiana continental slope have produced data derived from high-resolution geohazards surveys which indicate that enormous volumes of authigenic carbonates are present. Geochemical analyses of these carbonates show a wide range of mineralogies as well as 6 13C values (?-25 to -55 ? PDB) indicating an origin from microbial oxidation of hydrocarbons. Broad variation in 6 13C values is thought to pnmari1y reflect various parent hydrocarbons ranging from biogenic methane to thermogenic gas and crude oil. Recent research submersible work in two areas known for extensive carbonate seafloor, Green Canyon Blocks 52-53 and 184-185, has confirmed considerable variability of seafloor features related to authigenic carbonate production. Authigenic carbonates range from small nodules in unconsolidated slope sediments to massive buildups in excess of 60 ft (-20 m) vertical relief. A complete spectrum of intermediate forms between these extremes was observed during submersible operations, suggesting a wide range of seafloor conditions and geotechnical and/or engineering properties. In addition to the fact that these carbonates are geologically important because they represent salt dome cap rocks in early stages of development, slope carbonates present substantial challenges for planning drilling/production platform placement, and for pipeline routing. Although high resolution seismic and side-scan sonar data have been used to identify areas of carbonate seafloor, their signatures are frequently similar to mud mounds and other soft-bottom features. Positive identification of carbonate hardgrounds, their relief, and their thicknesses may be difficult using typical remotely sensed hazard survey data. Observations from the submersible, for example, suggest that the topographic variability of carbonate buildups over shallow subsurface salt diapirs is much more dramatic and complex than analysis of seismic and side-scan records has previously indicated. INTRODUCTION A project sponsored by NOM National Undersea Research Center (Wilmington, North Carolina) provided the opportunity to investigate "rough seafloor" areas that typically occur above shallow salt diapirs of the Louisiana continental slope. A Pisces II research submersible (Fig. 1) was used to make direct observations of these areas and collect rocks, and sediments related to specific seafloor features. Although other researchers have used submersibles to study Louisiana's slope, their objectives have been focused primarily on identification of oil and gas seeps as well as the chemosynthetic communities that frequently are associated with hydrocarbon vents [1,2,3,4]. The project on which this paper is based was designed to develop an understanding of the geological and geochemical products of seep areas, primarily the authigenic carbonates. Although previous studies of the slope [5,6,7] recognized its bathymetric and structural complexity as a product of salt tectonics, the vast areas of carbonate-rich sediments and seafloor buildups which are also largely localized by saltrelated features have generally escaped detailed investigation. However, as the oil and gas industry moves into deeper water these areas must receive more attention. In response to this need a number of recent studies [8,9,10,11] have emphasized the widespread abundance of carbonate sediments and buildups on the Louisiana slope.
- North America > United States > Louisiana (1.00)
- North America > United States > North Carolina > New Hanover County > Wilmington (0.24)
- North America > United States > Gulf of Mexico > Central GOM > West Gulf Coast Tertiary Basin > Green Canyon (0.98)
- North America > Canada > Saskatchewan > Williston Basin > Delta Field > Shaunavon Formation (0.98)
Nearsurface Geology of the Gulf of Mexico Continental Slope
Coleman, J.M. (Louisiana State University) | Bouma, A.H. (Louisiana State University) | Prior, D.B. (Louisiana State University) | Roberts, H.H. (Louisiana State University)
ABSTARCT The continental slope of the Gulf of Mexico covers an area of more than 500,000 sq km. Consisting of smooth and gently sloping surfaces, prominent escarpments, knolls, intraslope basins, and submarine canyons and channels, it is an area of extremely diverse topographic and sedimentologic conditions. The slope extends from the shelf break, roughly at the 200-m isobath, to the upper limit of the continental rise at a depth of 2,800 m. The most complex province in the basin, and the one of most interest to the petroleum industry, is the Louisiana- Texas slope, which occupies 120,000 sq km and in which bottom slopes range from less than 1 degree to greater than 20 degrees around knolls and basins. In the past few years, numerous high-resolution seismic surveys, foundation borings, and drop cores have been acquired on the continental slope. They form the basis the interpretation of the nearsurface geologic framework. INTRODUCTION The complex Gulf of Mexico Basin was characterized during the Tertiary by an extremely large introduction of clastic sediment, mobilization of large salt masses, and formation of highly active penecontemporaneous or growth faulting. Mesozoic and Cenozoic sediments are estimated to attain a total thickness in excess of 15,000 m, the maximum zone of thickness trending east-west near the present day coastal plain of Louisiana and west Texas. Rapid subsidence associated with sediment loading has been responsible for such thick localized sedimentary accumulations. The Gulf Basin has been dominated, from the beginning of the Tertiary to present times, by the sediment yield of the Mississippi River (Martin and Bouma, 1978 Bouma et al., 1978). The submerge part of the Gulf Basin can be divided into several major regions or provinces the northeastern and eastern Gulf (Florida, Alabama, and Mississippi), the central Gulf (offshore Louisiana and Texas), the western Gulf (offshore west Texas and Mexico), and the Golfo and Banco de Campeche, along the southern rim of the Gulf (Figure 1). The Sigsbee Escarpment is the most prominent feature at the base of the slope, This escarpment is nearly continuous along the entire base of the slope from the western Gulf to De Soto Canyon. The scarp is the expression of the lobate frontal edge of the northern Gulf diapiric province and is underlain throughout its length by a complex system of salt ridges, overthrust tongues, and steepsided massifs (Humphries, 1978 Martin 1978, 1984). The continuity of the escarpment is broken locally by diapiric outliers and large, pronounced reentrant of several large interlobal canyons such as the Alaminos and Keathley. The nearsurface geology and topography of the slope is a function of the interplay between episodes of rapid shelf edge and slope progradation and contemporaneous modification of the depositional sequence by diapirism and mass-movement processes during late Wisconsin glaciation and lowered sea level.
- North America > United States > Texas (1.00)
- North America > United States > Gulf of Mexico > Central GOM (0.54)
ABSTRACT Rock wettability can be determined with wireline formation pressure measurements above, in, and below the transition zone of an oil-water contact, when other logging and petrographic data are available. A simple model based on capillary tubes qualitatively explains very well the behavior of the laboratory and field pressure data measured at interfaces in various conditions. Theoretical derivations of the pressure profile for strongly water wet, strongly oil wet, and neutral wettability rock are in fairly good agreement with laboratory experimental data. Fragmentary field data also seem to agree with the theory. Downhole measurements should be made for the purpose of estimating rock wettability using the proposed theory and for verifying the effect of filtrate invasion. It is also suggested that a new wireline formation tester be built and dedicated to the collection of closely spaced formation pressure data.
- South America (1.00)
- Oceania > Australia (1.00)
- North America > United States > Oklahoma (1.00)
- (16 more...)
- Government > Regional Government > North America Government > United States Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Lloyd Ridge > Block 50 > Atlas Field (0.99)
- Europe > United Kingdom > North Sea > Central North Sea > Kittiwake Area > Block 21/18 > Fulmar Formation > Eagle Well (0.98)
Technical Advances in High-Resolution Hazard Surveying, Deepwater Gulf of Mexico
Prior, D.B. (Louisiana State University) | Doyle, E.H. (Shell Oil Co.) | Kaluza, M.J. (Fugro McClelland) | Woods, M.M. (Fugro McClelland) | Roth, J.W. (Shell Offshore Inc.)
ABSTRACT High-resolution geophysical techniques are now capable of routine assessment of sea-floor geology relevant to oil and gas exploration and production in the Gulf of Mexico to water depths of 7700 ft. Survey methods pioneered in deepwater areas off the Atlantic east coast have been significantly improved. Present practice uses satellite navigation for ship positioning and bottom-mounted telemetering transponder arrays for accurate positioning of deeply towed sensors. Deeply towed subbottom profiler and side-scan sonar systems provide very high resolution data for near-surface sediments and seafloor morphology. Digital recording provides capability for real-time image processing and enhancement. Bathymetric mapping uses surface-towed narrow-beam fathometers calibrated for water column velocity and bottom slope. Medium-penetration seismic data are displayed through a control module to reduce vertical exaggeration and improve resolution. The new techniques allow comprehensive engineering geologic evaluations of deepwater prospects in a cost- and time-effective manner. INTRODUCTION A capability has been developed to conduct very accurate high-resolution geophysical surveys to water depths of 7700 ft in the Gulf of Mexico. The surveys define geologic constraints for exploration drilling, determine sea-floor and near-surface geologic conditions relevant to various deepwater production engineering options, and provide data for correlation with geotechnical properties for foundation design. Survey strategy and techniques are specifically designed to acquire sets of highly detailed acoustic data for prospects at various localities over the continental slope. This region exhibits great diversity in sea-floor relief, sediment properties, and geologic processes. For example, in inter-diapir areas bottom relief may reach 1000 ft, with slope gradients exceeding 20°. Near-surface sediments include sequences of parallel-bedded clays and silts resulting from Pleistocene slope progradation and deepwater sedimentation, but there are large variations in local sequence geometries and sediment consolidation properties. Geologic processes that influence local site characteristics include faulting, gas and fluid expulsion, clathrate formation, diapiric uplift and faulting, mass-movement phenomena, and sea-floor erosion. A systematic program for assessment of deepwater geology for engineering purposes was first employed in 1981-84 off the Atlantic east coast. 2 The methods include deep-tow 100-kHz side-scan sonar and 3.5–7.0 kHz subbottom profiling. Recent technical improvements, which are the subject of this paper, have resulted in both substantially enhanced data quality and efficient, comprehensive deepwater site mapping and geologic assessment. SURVEY STRATEGY The total suite of acoustic data for each prospect area is generated by two separate survey missions, each with its own objectives and tools. The first-phase effort focuses upon acquisition of precision bathymetric profiles using a 24-kHz narrow-beam echo-sounder (Edo-Western 4077). Simultaneously, both sparker (8.4 kjoules) and minisparker (300 joules) profiles are collected to provide a complete overview of the subsurface stratigraphy and structure of the area, typically to depths of 1500–2000 ft and 300–600 ft, respectively, below the sea floor. Sediment sequence geometry and associated features such as faults, diapirs, subsurface gas, buried channels, and mass-movement features are identified from these data. Survey grids comprise 980-ft line spacings (primary) with 2950 oft tie lines. The grid orientation is predetermined using available regional data to give optimum coverage of local g
- Geology > Structural Geology > Tectonics > Salt Tectonics (0.44)
- Geology > Sedimentary Geology > Depositional Environment > Marine Environment (0.34)