This work evaluates the economics of GTL plant using two synthesis gas methods. The first method called the base case utilizes oxygen as fuel for combustion of natural gas, while the proposed case uses steam/CO 2 instead of Oxygen. The aim is to ascertain a more economically viable GTL configuration for an optimal GTL process. The associated flare gas at Egbema production sites in the Niger Delta has been chosen as case study. The gas flowrate is 50MMscfd of raw natural gas which was pre-treated before being fed into the main GTL plant. The liquid yield result shows that the proposed method has a liquid yield of 5730b/d over the 5430b/d gotten from the base case representing an increase in product yield of 5.5%. The economic analyses show a quicker pay-out time of 4.9 years from the proposed model compared to 5.9 years from the base case. Using the proposed method gave an annual cashflow increase of 20.9% and NPV increase of 59.7% at 10% discount rates. Also the DCF-ROR from the proposed method was 20.3% compared to 16.6% gotten from the base method. Thus the proposed method is more profitable in terms of NPV. The project is recommended for application in the Niger Delta stranded and remote gas locations that have before now been subjected to flaring.
The mechanism of buckling has been extensively studied in pipes and tubings. But these studies more often has been restricted to continuous or straight body pipes. In reality most pipes and other drillstring elements have end couplings or connections known as tool joint. Tool joint presence changes the annular geometry, hydraulics and stress distribution of the pipe or tubulars in the wellbore. Modelling drillstring in highly deviated wells with no regards to the tool joint effects has been a major source of error in many drilling mechanics analysis. This has often led to misleading information on buckling and bending of the pipe which could lead to drilling and completion problems and costly well interventions. Thus it becomes necessary to model tool joint effect in the drillstring as it is subjected to downhole forces and stresses. In this study, emphasis is made on the determination of tool joint effect on pipe buckling for highly deviated extended reach wells (ERWs). WellPlan T&D spreadsheet software was used for the simulation. The simulation was runned for pipe with tool joint and the same pipe with the tool joints removed. Results show that jointed pipes has similar buckling behaviour with continuous straight body pipes with buckling starting from sinusoidal buckling mode and gradually entering the helical buckling mode for both types of pipes. Furthermore, result revealed that tool joint presence increases the critical buckling force by an average of 28.9% for helical as well as (AWA) sinusoidal buckling modes.
In order to counterbalance the formation pressure, the drilling mud is weighted up using a chemical additive, usually Barite. The usability of locally sourced Nigerian Barites on the major types of drilling fluids in conventional conditions is presented. Water-Based mud, Oil-Based mud and Synthetic-Based mud formulations with locally sourced Barite were tested according to the American Petroleum Institute recommended practices. Hole cleaning capabilities of the formulations by the use of Cutting Carrying Index (CCI) and Cutting Concentration (CC) as indicators showed that Osina, Gabu and Obubra Nigerian Barites are suitable for use as drilling fluid additives; with Cutting Carrying Index in the range of 23.27 to 120.54 for Water-Based mud, 0.89 to 3.98 for Oil-Based mud and 0.45 to 1.13 for Synthetic-Based mud. The Cutting Concentration of average of 4.15 vol. % at 355gpm and 300ft/hr ROP for Water-Based mud, Oil-Based mud and Synthetic-Based mud, with MAXROP of 364ft/hr under the same conditions was recorded. Moreso, laminar flow regime in the annulus was predicted for all the mud types under the same conditions and temperatures specified, based on a MATLAB programme developed to perform the computation. Cutting Carrying Index for water based mud decreased from ambient, 120°F, 180°F to 240°F compared with API mud used as control sample.
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