Growth of 92 Finnish patients with 21-hydroxylase deficiency (21-OHD) was analyzed retrospectively to study growth both before the diagnosis and during glucocorticoid substitution therapy. The patients were divided into two groups: those diagnosed at infancy (56 patients) and those diagnosed after the age of 1 y (36 patients). Birth lengths of those boys and girls diagnosed at infancy were greater than the national mean birth lengths (p < 0.001). Mean relative length diminished from +0.8 SD score (SDS) at birth to -1.0 SDS by the age of 1 y. Adult height was -1.0 SDS (159.9 cm) for women and -0.8 SDS (173.6 cm) for men. The difference from national mean height was significant only for women (p = 0.026). Mean relative weight during childhood correlated negatively with adult stature (r = -0.620; p = 0.006). In the group of children diagnosed later in their childhood, growth was already accelerated at infancy from +0.2 SDS at birth to +0.7 SDS by the age of 1 y (p = 0.023). The final height of girls diagnosed later in childhood was within normal limits (-0.5 SDS; 162.1 cm), whereas it was low in the corresponding group of boys (-2.1 SDS; 165.3 cm). Our data show increased mean birth length in babies with early diagnosis of 21-OHD and growth acceleration at infancy in children diagnosed later in their childhood, reflecting the growth accelerating effect of adrenal hyperandrogenism early during fetal life and infancy. To improve final height in patients with 21-OHD, lower doses of hydrocortisone should be used at infancy, and special attention should be paid to boys diagnosed later in childhood.
A method has been developed that allows the estimation of porosity as a function of reservoir depth in high vertical relief fields. Porosity is known to decrease as net overburden pressure increases. This porosity reduction in turn leads to large reductions in reservoir permeability, the end result being a significant reduction in productive pore volume, net pay, and well productivity. The Eastern Overthrust Fields in Venezuela's El Furrial Trend produce from thick Miocene to Cretaceous sandstones and have very large hydrocarbon columns (two to three thousand feet is not unusual). Therefore, significant deterioration in pay quality is observed in the downdip areas. Using data from wells drilled in the Repsol/YPF Quiriquire Block, we observed that it was difficult to understand the true nature of the reservoir sands because the data was distorted by reservoir compaction in downdip wells. A method was developed to eliminate the distortion introduced by depth and overburden stress in porosity logs. This technique allows the well data to be interpreted as if all the wells had been drilled at a common datum. Once the undistorted data is interpreted and contoured, the data is re- shifted up or down using a depth grid map. Reservoir property grid maps can be prepared which better represent the sandstone properties at the depth at which they are found today. These maps can then be used in reservoir simulators to match and predict reservoir volumes and performance. The proposed method is most useful in development situations where there is sparse well control. Therefore, our first application has been in the Repsol/YPF operated Tropical Field, a 1998 discovery. Using this method, we prepared a reservoir description that depicts undrilled downdip areas much more accurately than would be possible using conventional methods. The new method resulted in large changes in our estimates of hydrocarbons in place and reserves and significantly impacted future development plans. Introduction High vertical relief reservoirs with large hydrocarbon columns present unique difficulties in reserve analysis and development planning. Fields with these characteristics are often found in the highly complex thrust belt regimes of the world including fields in Colombia, Bolivia, Argentina and Eastern Venezuela. A significant problem associated with having thousands of feet of vertical closure is the potential for compaction of the reservoir rock with depth, resulting in diminished pore volume and permeability. This adversely impacts reserve calculations and development strategies. For example, reservoir rock on the deeper fringe of the structure may have lower porosity and much reduced flow capacity, with the result that wells drilled in these areas will not flow at rates exhibited by wells drilled on the crest of the structure. Likewise, blanket estimations of reserves based upon crestal wells will yield optimistic values of reserves. We have also observed a tendency for geostatistical software to yield fairly unreliable geologic models unless it is programmed to account for porosity changes with depth. These reservoir description and engineering problems are highly compounded during the early reservoir appraisal and development phases. The Tropical Field in Eastern Venezuela is a recent discovery, and an excellent example of such a case.
The Quiriquire Deep Field located in the Eastern Venezuela is a large and complex compartmentalized accumulation, with a hydrocarbon column of some 3,500 ft. (3000 ft in the gas cap and 500 ft in the oil rim). The appraised part of the field has an estimated 2.0 TCF of Original Gas in Place both free and associated, and 550 MMBO (50 MMBO from the gas cap and 500 MMBO from the oil leg). There is a very significant variation with depth of the stock tank oil API and the standard gas/stock tank oil ratio within the fluid column both in the gas cap and the oil legs (>50 °API to <15 °API). The multidisciplinary study included a static numerical representation of the geological model, taking into account all available information and integrating the vertical communication among formations and the reservoir compartmentalization as inferred from the available performance/dynamic data (mainly pressures, production tests and fluid types). Given the very limited dynamic information available and the limitations of seismic imaging in this area, a History Matched coarse grid simulation model was used as a Material Balance tool to study reservoir compartmentalization; evaluate volumes in place per compartment; and estimate well counts and overall recoveries for alternative development scenarios. A key part of the model was an accurate representation of the complex PVT behavior, including depth profiles of oil content in the gas, oil API gravity and initial Rs; as well as GOC depth estimates for each compartment. The study supports the blowdown of the gas cap as the most commercially attractive and less risky development strategy. Introduction The Quiriquire Deep Field located in the Eastern Venezuela basin [discovered by Creole (ESSO) in 1952] is a complex compartmentalized accumulation with 3,500 ft of hydrocarbon column (3000 ft in the gas cap and 500 feet in the oil leg). The Quiriquire Deep Field structure is a SW to NE trending thrust anticline (formed during late Oligocene to Early Miocene) 18 Km long and 3.5 Km wide with around 4,300 ft of vertical relief. The anticline is controlled by a back thrust and a steep forelimb and is crossed by a series of steeply dipping normal faults, which in some cases cause pressure seals that compartmentalize the structure (Fig. 1). The target reservoir sandstones range in age from Cretaceous to Late Oligocene. The Hydrocarbon Fluid Column is quite complex. Both the oil leg and the condensate from the gas cap have an important variation of API and gas oil ratio with depth. Several attempts to develop the oil leg in the past have had limited success, mainly due to diminishing API with depth in the oil rim, the complex stratigraphy, and the sometimes poor rock properties (specially in the deeper formations). The Material Balance simulation model built in this study support the blowdown of the gas cap as the most attractive development strategy. Static Model The reservoir targets in Quiriquire Deep are mainly inter-bedded marine sandstones, ranging in age from Upper Cretaceous to Late Oligocene, with porosities rangng from 4 to 12% and permeabilities between 0.1 to 100 md. The main productive formations in Quiriquire Deep (as illustrated in Figure 2) are: Los Jabillos (Late Oligocene); Caratas (Eocene), Vidoño (Paleocene), San Juan (Cretaceous), and San Antonio (Cretaceous), which were correlated using Maximum Flooding Surfaces as markers, as identified in the electric logs adjusted with micropaleontology data. A static model using a geocellular approach was built with the information from 29 wells (Vsh, porosity and Sw), structural maps representing the various formations of the stratigraphic column, and fault planes. The final geocellular model contained over 700,000 cells. Fig. 3 shows a cross section from the static model displaying the Vsh attribute to illustrate the high the degree of heterogeneity that exists.
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