Drainage Of Reservoir Research Articles

Evaluation and Management of Vertically Drained Reservoirs: Castilla and Chichimene Fields, Llanos Basin, Colombia: ABSTRACT

The Castilla and Chichimene NE fields, operated by Chevron, are located in the southern Llanos basin of Colombia. The Castilla field, with an estimated 2.3 billion BBLS OOIP, produces heavy 14{prime} API oil, while the Chichimene NE field with an estimated 480 MMBBLS OOIP, produces a lighter 20{prime} API oil. Production is from multiple sandstone reservoirs of the Tertiary San Fernando and the Cretaceous Guadalupe Formations, and from massive non-marine sands of the Cretaceous Une Formation. Early problems with water coning and high water cuts led to detailed geologic study and engineering simulation to determine the most effective methods of reservoir management. The fresh nature of the connate water made evaluation more complicated, but results of RST (Reservoir Saturation Tool) logging runs on producing wells support the conclusions of the simulation studies regarding the potential for vertical drainage of the reservoir. As a result, the massive sands of the Une Formation can be perforated in the upper portion of the reservoir only, still enabling effective drainage of the lower reservoir while reducing water production and coning problems.

Tunnel-valley formation in northwest Germany—geology, mechanisms of formation and subglacial bed conditions for the Bornhöved tunnel valley

The Bornhöved tunnel valley consists of a relatively broad, elongated depression filled primarily with tills, and a narrow channel in the axial part filled with outwash, glaciolacustrine sediments and tills. The tunnel valley is at least 13 km long, 222 m deep (bottom at 191 m b.s.l.), and extends parallel to the axis of a peripheral sink between two Permian salt diapirs in the substratum. It is suggested that the initiation of the tunnel valley was controlled by a differential response of the bed materials to ice overriding on top of and between the salt structures. The Bornhöved tunnel valley is a polygenetic feature that resulted from different erosional processes throughout all three main glaciations in northern Germany. During the Elsterian Glaciation glaciotectonic squeezing occurred, to be later replaced by subglacial meltwater erosion. During the ice retreat and the Holsteinian Interglacial, the valley was filled with fine-grained glaciolacustrine and marine sediments, which were subsequently removed and redeposited further down-ice as a 200-m-thick glaciotectonic melange by the first Saalian advance. The second Saalian advance caused only minor changes and the tunnel valley was reactivated as a subglacial channel during the Weichselian Glaciation. It is suggested that at the time of the first Weichselian ice advance a large subglacial water reservoir developed in the area of the Baltic Sea basin and caused a rapid, surge-like ice movement. As the ice sheet advanced out of the Baltic Sea basin, drainage of the water reservoir was prevented by the ice toe overriding the permafrost on the Saalian highlands. During the ice retreat, frozen ground was left beyond the ice margin and subglacial meltwater catastrophically drained through the tunnel valley with a discharge roughly estimated at about 3.75 × 10 3 m 3/s. It seems possible that drainage of the subglacial water collector through the Bornhöved tunnel valley and other similar channels south of the Baltic Sea led to increased ice-sheet basal friction, and was one reason for successively smaller extents of the subsequent Weichselian advances. Evidence against pervasively deforming bed materials in the vicinity of the Bornhöved tunnel valley in the Weichselian Glaciation indicates that the valley served as an efficient drainage path for porewater from the subglacial sediments.

Role of Bedrock Ground Water in the Initiation of Debris Flows and Sustained Post-Flow Stream Discharge

Numerous debris-flow events occurred along the Wasatch Front near Salt Lake City, Utah, during the springs of 1983 and 1984. These flows were distinctly different from the previous damaging flows of 1923 and 1930 which were related to cloudburst thunderstorms. The 1983 and 1984 flows were related to the rapid melting of an above average snow pack. These flows originated as localized failures of colluvial sediment on the upper slopes of the Wasatch Front which had developed on a Precambrian metamorphic bedrock. Following the debris-flow event, “normally dry streams” continued to flow well into the autumn. These sustained flows suggest drainage of a ground-water reservoir, “tapped” by the slope failure and scour of the channel. The supply of ground water contained within the colluvium could not sustain the observed stream flow at the canyon mouth. Therefore, we believe that a bedrock reservoir provided the source of water for sustained stream discharges. Field observations and mapping indicate that the metamorphic bedrock has been highly fractured. Erosion control and range management practices following the 1930 debris-flow events combined with a gradual recovery of the Salt Lake area moisture balance effectively recharged this bedrock aquifer. Excess recharge during the rapid spring melt overcharged the bedrock aquifer, increased the pore-water pressure in the colluvium at locations of bedrock springs and seeps, and led to localized slope failures which mobilized the down canyon colluvium into debris flows. Drainage of the bedrock aquifer, at exposed springs and seeps, maintains the sustained stream discharge seen at the canyon mouths.

The Svartsengi reservoir in Iceland

The Svartsengi geothermal reservoir in Iceland is described and its production history presented. Lumped-parameter models for confined and unconfined reservoirs are derived, and a conceptual model of the reservoir suggested. Using depletion analysis, the dominant production mechanism is identified as drainage of an unconfined reservoir.

Surgical treatment of hydrocephalus in children. II. Complications

The authors analized the complications of fifty seven children with hydrocephalus due to congenital malformation (42.1%), meningitis (36.8%) and tumor (21.1%), that were submitted to surgical treatment for hydrocephalus, from 1970 to 1980. External ventricular drainage and insertion of ventriculostomy reservoir were used to control the expanding hydrocephalus in children with meningitis. Complications weren't observed in the first procedure. Cutaneous abscess, brain abscess, cerebrospinal fluid leakage, wound dehiscence, malposition of the reservoir and local tumor were observed in the use of the ventriculostomy reservoir and these complications caused a revision rate of 0.47 revisions per patient. Hypothalamic ventriculostomy with catheter showed complications (catheter obstruction and meningitis) that caused a revision rate of 0.57 revisions per patient. Ventriculoatrial shunting procedure showed several complications (malposition of the distal catheter, malfunction of the valvular system without obstruction and infection and thrombosis of the superior vena cava), that caused a revision rate of 0.57 revisions per patient. Ventriculo-peritoneal shunting procedure showed infections in 30.8%, malfunction of the valvular system in 32.2% cerebrospinal fluid leakage in 17.3%, malposition of catheter in 13.5%, catheter disconnection in 9.6%, transient abdominal distension in two cases and overdrainage phenomena, ascites and abdominal pseudocyst in one case.

Prevention of peritonitis after cystectomy in patients with bladder neoplasms

Analysis of the immediate results of cystectomy in 159 patients showed that, in order to prevent peritonitis after cystectomy with ureterocoloanastomosis, it is advisable to combine intraoperative novocaine blockade of the nervous intermesenteric tract with ureter transplantation into the sigmoid part of the intestine below the sacro-lumbar joint or into the rectum, the rectum. In operations of bladder replacement with an intestinal graft (122 patients), a double-row uretero-intestinal anastomosis and suprapubic drainage of the intestinal reservoir are recommended. This significantly reduces the possibility of developing urinary peritonitis.