IntroductionDrilling cost optimization has always been, and will continue to be, the most important issue in the petroleum drilling industry. Using slim hole technology is one of the sure ways to achieve substantial cost savings. The basic difference between conventional wells and slim hole wells is the wellbore geometry. While the hole diameter of the production interval in a conventional well ranges from 6½ in to 9 5 /8 in, that of a slim hole well ranges from 3½ in to less than 6 in. Recent advances (1)(2)(3) in slim hole technology include the development of drilling fluids to reduce the APLs because 60% of the pressure loss occurs in the annulus of slim hole wells (1) .Some developments in slim hole drilling fluids design have included the works of Downs et al. (2) They formulated formate brinebased fluid with xanthan gum as a viscosifier. Randolph et al. (3) developed a unique weighting agent for slim hole drilling. In general, low solids-fluids are used to prevent the plating out of solids inside the drill string, and the fluids should have low viscosity to avoid an excessively large equivalent circulating density (ECD). These systems are very costly, thereby reducing the cost savings significantly. The purpose of this study was to develop a low-cost, low viscosity fluid that will reduce the annular pressure loss significantly while maintaining a gauged hole. Study MethodologyThis study involved the development of several fluids and their rheological characterizations with Bingham Plastic and Power Law models. The data were used for calculating APL gradients for three slim hole geometries and carrying capacities of the fluids. The fluids developed were water-based because they are cheap, environmentally accepted and they require little effort when detecting gas kicks. Two main groups of fluids were tested: bentonite (clay)-based fluids and viscosified brines. Salts were added to the fluids for wellbore stability. The two types of salts used in this study are potassium chloride (KCl) and potassium formate (KF). Xanthan and PHPA (partially hydrolyzed polyacrylamide) polymer were used as viscosifiers in the brines in order to investigate their effects on annular pressure losses. In all fifty-three (53) study samples, different fluids were formulated under atmospheric conditions and at 150°F. Tables 1 and 2 show the compositions and rheological parameters of selected fluids tested under atmospheric conditions and at high temperature.Thirty fluids exhibited Power Law behaviour while the remaining 23 exhibited Bingham Plastic behaviour. All brines with PHPA seemed to exhibit Bingham Plastic behaviour, while all brines with xanthan exhibited Power Law behaviour. The APL gradients were calculated using the rheological data from the two models. Table 3 lists the equations for estimating APL in the annulus for the two models. The pressure calculations were performed for flow rates of 22.2 gpm, 34.6 gpm and 100 gpm, and three wellbore geometries. The carrying capacities of the fluids were evaluated using the slip ...

Four major factors affecting horizontal well gravel pack were studied using a 3D simulator developed for horizontal well gravel packing. The factors included settling effect, gravel concentration, injection rate and carrier fluid viscosity. Three actual field horizontal well gravel pack jobs obtained from the literature were performed using the simulator to study these factors. The effect of carrier fluid viscosity on gravel pack efficiency was studied by varying the viscosity between 1 and 51 cP, injection rate between 0.159 and 0.636 m3/min and gravel concentration between 0.50 and 4.0 pound mass per gallon. Simulation results demonstrate the validity of the solution routine and the capability of the simulator, because the results were in agreement with the field results. The predicted pack efficiency for cases that considered settling effect are consistently higher than the cases without settling effect. The study also showed that the settling factor decreases with increasing gravel concentration and injection rate. Introduction Several authors have investigated the factors affecting gravel transportation and placement towards achieving an effective gravel pack. Gruesbeck et al.(1) performed experiments to measure pack efficiency as a function of screen parameter, fluid and gravel properties, completion configuration and angle of inclination of the wellbore. They concluded that packing efficiency increases with lower gravel concentration, lower gravel density, higher flow rate and increasing resistance to fluid flow in the tailpipe/screen annulus. Hodge(2) substantiated Gruesbeck et al.'s work by determining the accuracy of the predicted equilibrium bank height. Elson et al.(3) reported a study conducted to define optimum gravel pack procedures and completion design factors for high angle wells. Results of the study showed that high viscosity carrier fluids with high gravel concentration provide good gravel transport, but are unsuitable in wells with angles of 80 º from vertical. Skaggs(4) presented the results of a large-scale vertical wellbore model he used to study gravel transport through perforations during a high-density squeeze gravel packing operation. He concluded that the transport efficiency through perforations increases with increased fluid viscosity, gravel concentration and annular velocity. Winterfeld and Schroeder(5) developed a finite element numerical simulator and used it with a full-scale wellbore model to study gravel placement in perforations and annulus. Their model was based on mass and momentum conservation equations, as well as those for vertical wells. Peden et al.(6) developed some mathematical design models for predicting the optimum combination ofrequired design parameters, such as tailpipe diameter, slurry flow rate and gravel concentration, for an optimum packing efficiency. These models were based on extensive experimental study of factors affecting packing efficiency and dimensional analysis of obtained data. In 1988, Wahlmeier and Andrews(7) improved on the earlier works of Gruesbeck et al. and Peden et al. by developing a pseudo-three-dimensional mathematical model suitable for designing and evaluating gravel pack treatments. Shryock(8) worked on a full-scale deviated model and had similar conclusions with earlier works.

Natural gas is a versatile form of non-polluting fuel. With just over a dozen nations accounting for 84% of the worldwide production, access to natural gas has become a significant factor in international economics and politics. The major difficulty in the use of natural gas is transportation and storage because of its low density. Despite this, natural gas production has seen tremendous growth over the years. This has been due to large amount of natural gas reserves, the wide variety of uses of natural gas and carbon dioxide emissions from natural gas energy generation are far less.In the past, the natural gas recovered in the course of producing petroleum could not be profitably sold, and was simply flared. This wasteful practice is now illegal in many countries. The most common method for transporting natural gas was high pressure in underground pipelines. Additionally, countries now recognize that value for the gas may be achieved with LNG, CNG, or other transportation methods to end-users in the future. In many cases the gas is now re-injected back into the formation for later recovery. Transportation is now a very important and key role in the supply chain for natural gas and the big challenge is to transport gas to markets at the lowest cost without too much environmental risks. Now re-gasification at the market is important when selecting the mode of transportation of natural gas. This paper reviews, analyzes and provide insight to present and future gas transportation methods. These options of transporting gas from oil and gas field to markets include pipelines, liquefied natural gas, compressed natural gas, gas to solids (hydrate), gas to liquids, gas to wire and other gas to commodity methods. The paper provides an overview of the challenges facing present transportation modes, and discussion on possibilities for improvement via new technology or new gas transport options. Another focus of the paper is to compare and highlight some critical factors affecting the different means of transportation of natural gas. These include economics, markets, gas concentrations, environmental risks and regasification issues.

No abstract

Four major factors affecting horizontal well gravel pack were studied using a 3-D simulator developed for horizontal well gravel packing. The factors include settling effect, gravel concentration, injection rate, and carrier fluid viscosity. The gravel pack process was simulated and the effectiveness and pack efficiency of the gravel pack job is determined using the simulator. The effect of carrier fluid viscosity on gravel-pack efficiency was studied by varying the viscosity between 1 and 51 cp, injection rate between 1 and 4 barrel per minute, and gravel concentration between 0.50 and 4.0 pound mass per gallon. These three factors affect the settling factor of the gravel as it enters the horizontal section which subsequently affects the pack effciciency of the gravel pack process. Introduction Several authors have investigated the factors affecting gravel transportation and placement towards achieving an effective gravel pack. Gruesbeck et al1 performed experiments to measure pack efficiency as a function of screen parameter, fluid and gravel properties, completion configuration and angle of inclination of the well bore. They also developed a model to determine the height of the equilibrium bank formed during gravel packing of an inclined well bore. They concluded that packing efficiency increases with lower gravel concentration, lower gravel density, higher flow rate and increasing resistance to fluid flow in the tail pipe/screen annulus. They contended that by increasing the ratio of tail pipe diameter to the inside diameter of screen beyond 0.6, better efficient packing could be achieved. Several successful jobs were reportedly performed with this philosophy. Carrier fluid of viscosity less than 10 cp produced an equilibrium bank that allows complete filling of the well bore when the bank height is less than the diameter of the casing. Hodge2 substantiated the Gruesbeck et al. work by determining the accuracy of the predicted equilibrium bank height. Elson, et al3 reported a study conducted to define optimum gravel pack procedures and completion design factors for high angle wells. Result of the study showed that high viscosity carrier fluids with high gravel concentration provides good gravel transport, but are unsuitable in wells with angles of 80o from vertical. Satisfactory transport and improved packing were achieved with lower carrier fluid viscosity and sand concentrations. Tailpipe design requirement recommended by Gruesbeck et al. was used with satisfactory results. Skaggs4 presented the result of a large-scale well bore model he used to study gravel transport through the perforations during a high-density squeeze gravel packing operation. He concluded that the transport efficiency through perforations increases with increased fluid viscosity, gravel concentration, and annular velocity. His work is however based on vertical well bore. Winterfeld and Schroeder5 developed a finite element numerical simulator and used it with a full-scale well bore model to study gravel placement in perforations and annulus. Their model is based on mass and momentum conservation equations. Peden et al6 developed some mathematical design models for predicting the optimum combination of required design parameters such as tailpipe diameter, slurry flow rate, and gravel concentration for an optimum packing efficiency. These models were based on extensive experimental study of factors affecting packing efficiency and dimensional analysis of obtained data. Wahlmeler and Andrews7 in 1988 improved on the earlier works of Gruesbeck et al. and Peden et al. by developing a pseudo-three dimensional mathematical model suitable for designing and evaluating gravel pack treatments. The pseudo-three dimensional model was based on overall aspects of well bore configuration and the mechanism involved in the process of gravel packing. The model was verified both with large-scale laboratory studies and field results Shryock8 worked on a full scale deviated model and had similar conclusions with earlier workers. He discovered that water carrier fluids completely gravel pack well bore deviated at 60o from vertical and that packing efficiency can be improved by increasing the resistance to flow in the liner-tailpipe annulus.