No abstract

Spur-dikes are efficient hydraulic structures that are made for numerous purposes. They have one end on the stream bank and another extending into the current. As a result of the existing spur-dikes in the stream course, the local scour phenomena usually occur around them, leading to several predicaments which have been of great concern to the hydraulic engineers. For the present work, laboratory experiments were carried out to measure the scour depths around several spur-dikes located at different distances for the V-shaped one. The experiments were conducted using physical models installed in a non-curved flume with a bed with uniform cohesion-less sediment of a medium particle size (d50 = 0.7 mm). All the models were operated under the subcritical flow of clear-water conditions. The investigations include three spur-dikes (1, 2 and 3) and three distances between them (1, 1.5 and 2 of spur-dike length) as two countermeasures to minimize the local scour depths. The results showed that an increasing number of spur-dikes and the distances between them would decrease the scour depths within the limit of the present study. The experimental data were used to create a new formula of R2 = 0.954 that reflects a good agreement with the experimentally observed results.

This work encompasses redevelopment of a supergiant southern Iraqi oil field from fully vertical to primarily horizontal wells. The subject reservoir is a massive world-class carbonate limestone reservoir containing 23 °API oil and is the dominant reservoir in a set of vertically stacked reservoirs. This reservoir is a part of a large anticline which is oriented north-northwest. The formation is Middle Cretaceous and has a subsea depth of 2100–2600 m. The reservoir was initially developed on a 200 acre inverted 9-spot pattern, and was on primary oil production until reservoir pressure dropped and production declined. Later, water injection started at centers of the 9-spot pattern. Development drilling was projected with future addition of vertical infills at 100 and then 50 acre patterns. During pressure drop due to primary production, water encroachment from flanks occurred, particularly, in the thin super-high permeability (vuggy) layers present in the reservoir; however, this was not clearly evident at early stages. By the time of starting pattern water injection with comingled injection and production in vertical wells, there was clear evidence of rapid water movement in the vuggy layers. As water injection progressed, the severity of watercut evolution in vertical wells rapidly progressed, necessitating change of the depletion plan. Continued development of the field with vertical infills would result in unsustainable water production and injection requirements, and lower oil recovery. A redevelopment effort was initiated to overcome these challenges. Geologic and simulation models were modified to reflect the evolved understanding of geology. Appropriate distribution of high permeability layers was introduced and calibrated to production data, in particular, water breakthrough timing and watercut evolution. The main change in the redevelopment plan has been to shift emphasis from drilling vertical infill wells to a fewer horizontal wells targeting low permeability zones which comprise most of the reserves. Reservoir development of the massive lower section is planned with 2 km long horizontal wells with injectors located in lower part of the reservoir and producers higher arranged in a line drive. Upper reservoir development is planned by working over existing comingled vertical wells to upper reservoir only thus decoupling upper and lower comingled production. The redevelopment plan achieves the business target rate with a much longer plateau duration at lower cost. The plan effectively utilizes existing vertical wells in addition to drilling new horizontal wells for recovering oil from lower, tighter reservoir. Initial performance of horizontal wells have shown very promising results with boosted dry oil production. This updated development plan is now in full execution phase and can provide redevelopment ideas for other brown fields with similar issues.

In this research, a study was conducted experimentally to investigate the scour hole dimensions downstream the combined structures which consist of weir and gate. Twelve models have been designed and every model is formed from composite weir consists of two geometric shapes and three types of gates which are rectangular, semi-circular and triangular in shape, where multi factors were studied to find out the effect of changing geometry for both weir and gate, discharge flowing in the flume and particle size of bed material on the dimensions of scour hole. The experiments was conducted in a laboratory channel was constructed from blocks and concrete with length of 18 m, 1 m width and 1 m depth. The laboratory models were installed after 7 m from the main gate which is controlling the passage of water from the main reservoir into the flume.At the beginning, the calibration process was conducted to identify the actual discharge values that pass in the flume, then experiments were conducted to calculate the discharge coefficient for each model, which represents one of the studied factors within the dimensional analysis of the variables to derive the empirical formulas to calculate the dimensions of scour hole.Then the experiments were conducted in order to derive formulas to investigate the depth and length of the scour hole which formed in the sand floor spreading as a layer of 30 cm in thickness for a distance 4 m downstream combined structure. Two samples of sand were used in the experiments with different median size of particles ( d50), the first of 0.7 mm and the second of 1 mm.Using the dimensional analysis by π theorem and IBM SPSS 21 program, Four nonlinear relationships were derived to calculate the dimensionless scour depth (SD / d50) and another four nonlinear relationships calculates the dimensionless length of scour (SL / d50)depending on the laboratory results for each of the relative discharge (Qr), Froude number in terms of mean size of particle of bed material (Frd), non-dimensional difference head between upstream and downstream of combined structure (HD / d50), dimensionless distance between the lower edge of the weir and the upper edge of the gate (y3 / d50), dimensionless head over the crest of compound weir (h/d50) and the discharge coefficient (Cd), where the resulted determination coefficients (R2) from these relationships were good.

Computational Fluid Dynamics (CFD) has been used to derive a mathematical model to relate the length of a gradual expansion (Le) with the others of hydraulic and geometric parameters of the flow in rectangular channels under supercritical flow conditions. Five models with different length of expansion 30 cm, 50 cm, 75 cm, 100 cm, and 125 cm were simulated in the CFD v18.2 software and verified by experimental data which have been measured into a laboratory flume. All models of CFD software were processed depending on k – epsilon viscous models while the mesh was built by adapting the multi-zone method. Five values of inlet velocity of flow were applied in the runs of the program to each model of 1.5 m/s, 1.6 m/s, 1.7 m/s, 1.8 m/s, and 2 m/s. Depths of water along the channel were measured in multi-section, before expansion, within expansion and after expansion. The results of CFD analysis showed that the minimum length of expansion to maintain the flow within supercritical regime was 0.35 m and the ratio of (Le/W) equal to 1.167. The results of the non-dimensional relationship were compared with the experimental results and the comparison showed a significant correlation where the highest percentage difference was 13.8 %. The coefficient of determination for this equation was 0.973.