Endpoint Mobility Ratios for Vertical and Horizontal Wells with Incidence of Scale Deposition

One of the most difficult and profit hurting problems found in the oil field is the build-up of scale deposits in the well bore, production string, flow lines and even in storage tanks. These deposits act as a restriction during build-up in the wellbore causing a gradual decrease in production and, in many cases, as a solid barrier for wellbore fluid flow. This paper presents an analytical model based on the existing thermodynamic model showing the endpoint mobility ratios for both vertical and horizontal wells with the incidence of scale precipitation and deposition at the near wellbore region during water flooding. The results revealed that Endpoint mobility ratio for a vertical well with radial flow approaches unity “1” faster than for the horizontal well with elliptical flow. And horizontal wells are good candidates for managing scale precipitation and deposition during waterflooding

MODELING OF WAX DEPOSITION DURING OIL PRODUCTION USING A TWO-PHASE FLASH CALCULATION

Wax deposition is a serious problem in the Petroleum Industry that results in the plugging of flow strings, formation damage, loss of hydrocarbons, increased production cost. The existing models used jn the oil industry for predicting wax phase equilibrium parameters over-estimate the amount of wax that is formed in terms of the wax weight fraction and the number of moles of solid. The Coutinho correlation is the latest of these models and is used to calculate the melting temperature and the enthalpy of fusion of the crude oil components. It did not consider the effect of branching of carbon atoms in the hydrocarbon structure/compound. But branching of carbon atoms in the hydrocarbon compounds affects its melting point. In this work, the correlation for calculating the melting temperature in crude oil developed by Coutinho has been modified to take into account the effect of branching of carbon-carbon chains in isoparaffins and the model has been used to calculate a new set of equilibrium parameter. The modified regular solution theory was used to calculate the activity coefficient ratio that was used as an input to the new model. Wax phase equilibrium flash calculations were carried out with the new set of equilibrium parameters. The wax mixture was then characterized using the weight fraction of component in the solid phase and weight fraction of component in the solid phase in the mixture. In order to check the reliability of the model, the data presented by Hanquan was used as input into the models developed by Won, Chung, Countinho and the new one. The new model predicted a more conservative value for the number of moles of solid formed, weight fraction of component in the solid phase and weight fraction of component in the solid phase in the mixture for C1s-C4o.This is an improvement over the existing models which overestimate the values of the parameters

EFFECT OF OILFIELD SULPHATE SCALES ON PRODUCTIVITY INDEX

The precipitation and deposition of scale pose serious injectivity and productivity problems. Several models have been developed for predicting oilfield scales formation and their effect on deliverability of the reservoir to aid in planning appropriate injection water programme. In this study an analytical model has been developed for predicting productivity index of reservoir with incidence of scale deposition in the vicinity of the well bore

Mobility Ratio Control in Water-flooded Reservoir with Incidence of Oilfield Scale

The process of precipitation and accumulation of oilfield scales around the well bore vicinity are major ongoing flow assurance problems that may result in formation damage. The phenomenon may negatively impact the success of a water-flooding project that majorly depends on mobility ratio. A predictive model has been developed for estimating the mobility ratio of a water-flooded reservoir with possible incidence of oilfield scale. Results show that the high mobility ratio encountered after water breakthrough does not only depend on the increase in water saturation and relative permeability but on the magnitude of oilfield scale saturation around the well bor

MODELING THE EFFECT OF TEMPERATURE ON ENVIRONMENTALLY SAFE OIL BASED DRILLING MUD USING ARTIFICIAL NEURAL NETWORK ALGORITHM

Due to increase in environmental legislation against the deposition of oil based mud on the environment, drilling companies have come up with an optimum drilling mud such as plant oil based mud with little or no aromatic content, which its waste is biodegradable. Optimum mud carry out the same function as diesel oil based drilling fluid and equally meets up with the HSE (Health, safety and environment) standard. It is expedient to determine the down hole mud properties such density in the laboratory or use of available correlation but most time; the range of data is not either reliable or unavailable. In this study, artificial neural network (ANN) was used to address the unreliable laboratory data and unavailable correlation for environmentally friendly oil based drilling mud such as jatropha and canola oil. The new artificial neural network model was developed for predicting the down hole mud density of diesel, jatropha and canola oil based drilling mud using 30 data sets. 60% of the data were used for training the network, 20% for testing, and another 20% for validation. The test results revealed that the back propagation neural network model (BPNN) showed perfect agreement with the experimental results in term of average absolute relative error returne

Elemental Sulphur Induced Formation Damage Management in Gas Reservoir

Sulphur compounds are considered as the most hazardous non-hydrocarbons in reservoir fluids, because of their corrosive nature, deleterious effects of petroleum products and tendency to plug porous medium which may impair formation productivity. Precipitation and deposition of elemental sulphur within reservoirs, near well bore region may significantly reduce the inflow performance of sour-gas wells and thus affect economic feasibility negatively. Studies have sought that almost all deep sour reservoirs precipitate elemental sulphur either occurring as a result of decomposition of H2S to give elemental sulphur or occurring as indigenous usually referred to as native sulphur as a dissolved species. Uncontrollable elemental sulphur induced formation damage has been one of the profit hurting syndromes that occurs in deep water sour gas reservoir. Meanwhile many correlations have been formulated thermodynamically to predict the occurrences of elemental sulphur but little information related to effect of its saturation on gas production and its corresponding formation damage. This paper presents an improved model for predicting elemental sulphur saturation and corresponding formation damage around the well bore. Results show that the minimum pore spaces blockage time was over-estimated by previous formulatio