Multilayered Oil Research Articles

Identifying Average Reservoir Pressure in Multilayered Oil Wells Using Selective Inflow Performance (SIP) Method

The downhole flow profiles of the wells with single production tubes and mixed flow from more than one layer can be complicated, making it challenging to obtain the average pressure of each layer independently. Production log data can be used to monitor the impacts of pressure depletion over time and to determine average pressure with the use of Selective Inflow Performance (SIP). The SIP technique provides a method of determining the steady state of inflow relationship for each individual layer. The well flows at different stabilized surface rates, and for each rate, a production log is run throughout the producing interval to record both downhole flow rates and flowing pressure. PVT data can be used to convert measured in-situ rates to surface conditions. Different types of Inflow Performance Relationship (IPR) equations can be used for SIP interpretation, including the Straight-line method, Fetkovitch method, and Laminar Internal Turbulent (LIT) relations. Although the SIP method can be used for single-phase flow, the interpreter can restrict the IPR’s calculations to a particular phase. This research discusses the difficulties in estimating the average reservoir pressure in multilayered reservoir completed wells over their production life. The SIP technique has been applied to some producing wells in the south of Iraq, which are completed in multiple producing reservoirs previously tested with a formation tester to estimate reservoir pressure and other parameters. Two wells are taken in the south of Iraq region, Zubair Oil Field, one with cross flow between perforations and the other well with no cross flow. An average pressure is not calculated for layer A in Well-1, because there is no contribution rate. While the average pressure for Well-1, layer B is 3414.49 psia. Also, the average pressure for Well-2, layer H is not calculated because there is no rate contribution from this layer, and the maximum average pressure was calculated in layer G, which is about 2606.26 psia. It is also found that the presence of cross flow has no effect on SIP calculations.

Economics of Combined CO2-EOR and CCS Projects Based on the Example of a Polish Multilayered Oil Field

Economics of Combined CO2-EOR and CCS Projects Based on the Example of a Polish Multilayered Oil Field

Problems and methods of hydraulic fracturing in multilayered oil reservoirs with the continuous perforation

One of the most common problems during hydraulic fracturing (HF) in the oil fields of Kazakhstan is a continuous perforation of all productive layers in the section of pay zone, which subsequently causes many risks of a different nature during fracking operations and difficulties in the development of oil reserves. Despite the historical reality, which is an actual problem, there are currently attempts to do fracturing in such difficult conditions. The main complicating factor is the formation of not one long fracture, but the development of several short fractures parallel to each other. This necessitates further development of technology in order to improve the efficiency of hydraulic fracturing.

Assessment of the Oil and Gas Potential of the Basement of the Southern Part of the Siberian Platform and Deep-Seated Oil Exploration

The main goal is to assess the oil and gas potential of the basement of the southern part of the Siberian Platform as an additional source for the long-term filling of the East Siberia–Pacific Ocean pipeline with hydrocarbons. The initial reserves in the fields, which were discovered in the sedimentary cover on the Siberian Platform, are far below the reserves of the fields of Western Siberia and the Volga Region, where the drilling of deep wells showed the connection of reserves with the basement; the reserves are renewed in a natural way. On the Siberian Platform, the drilling usually ended at the “cover–basement” boundary (at the most productive level). In the wells, there are the following signs that indicate the oil and gas potential of the basement: “black” zircons in granitoids containing radioactive elements, multi-layered oil reservoirs, which are associated with deep faults, and mantle fluids bearing hydrogen and liquid hydrocarbons. Based on the signs listed, which indicate the promising basement rocks, it is necessary to change the existing methods for prospecting and evaluating oil in the sedimentary cover and to focus on the exploration of heavy deep oil in the basement rocks.

Increasing the stimulation efficiency of heterogeneous carbonate reservoirs by developing a multi-bached acid system

Matrix acidizing is a common practice in the oilfield for minimizing formation damage through dissolution of the reservoir rocks and making appropriate wormholes. For obtaining the highest performance in the acidizing and stimulation treatments, the injecting fluid should be placed in the damaged zones of the reservoir layers, after which the easy flowback could fully improve the formation damage. In multi-layered oil reservoirs the fluid diversion becomes of paramount importance where preferential flow paths are adopted in most of the stimulation fluid and the zones, which have the lower values of the rock permeability, remain untreated.We develop an optimal multi-bached acid system in two steps by determining the diverter formulation and investigating the diverting characteristics of the acid system through core flood tests. The interfacial tension tests were conducted to determine the diverter (fluid packer) formulation. The effects of different concentrations and mixtures of organic acids, HCL and surfactant were investigated to find the most effective main batch (active batch) of the stimulation fluids. In the second experimental phase, the ability of the selected emulsified acid system as a fluid packer and diverter was investigated using the multi-bached acid system in a parallel core flood test. The results showed the efficiency of the emulsified acid system in diverting the second batch (active batch) of the stimulation fluid from the core with the higher permeability to the lower permeability one.We find that the developed multi-batch acid stimulation system is an advantageous technique to use for stimulating the multilayered wells where there is a big difference between the permeabilities of the producing formations. The permeablity improvement in a more uniform manner in both the layers proves the efficiency of the developed stimulation system and emulsion which used as a diverter. In addition, we detect that the mixture of 15%HCL and surfactant (GF – 15 MPS) with 0.5% concentration has provides the optimal reaction rate and dissolution rate in comparison with other mixtures studied by increasing the neutralization time.In short, firstly, in this work the acid distribution rate mechanism (pathway) between the reservoir layers was investigated by simulating the executed actual matrix acidizing operation in the considered well. Then, The self-diverting emulsified acid SDEA (which can be used as a diverter) was developed. Moreover, the main batch of stimulation fluid was developed by analyzing different acid mixtures with various concentrations. Lastly, the efficiency of the developed multi-bached acid system was evaluated by conducting the core-flood experiment. The results show that the developed multi-batch acid stimulation system is significantly efficient for stimulation of the heterogeneous carbonate reservoirs where there is a big difference between the permeabilities of the producing formations so that the stimulation of both layers (with different permeability values) can be accomplished in a more uniform manner.

Hydraulic fracture optimization by using a modified Pseudo-3D model in multi-layered reservoirs

The aim of hydraulic fracturing optimization is to maximize well productivity index by optimizing fracture geometry parameters. Height in geometry calculation is the most important parameter, especially in the multi-layered reservoirs due to the complexity of the in-situ stress distribution. A modified pseudo-3D model suggests a combination of unified fracture design (UFD), 2D fracture propagation models (PKN or KGD) and linear elastic fracture mechanic (LEFM) principle to achieve optimized fracture geometry. First, the LEFM principle has been used to obtain equilibrium fracture height associated with a calculated vertical pressure distribution along the in-situ stress and fracture toughness profiles. Then, the UFD concept in conjunction with 2D fracture models are used to obtain an optimum fracture target length, the corresponding net pressure, and the maximum dimensionless productivity index. This paper shows the insight of the new approach of hydraulic fracture optimization by using an efficient and practical algorithm in calculating equilibrium fracture height growth belong to certain treating pressure. The proposed model is applicable to broad-spectrum of multi-layered oil and gas reservoirs with more accurate estimation of final fracture height and treating pressure. Finally, two case studies have been used to represent that the model is effective and appropriate for practical purposes.

Development of double layered emulsion droplets with pectin/β-lactoglobulin complex for bioactive delivery purposes

The objective of the present study was to load piroxicam (PX) into multi-layered oil in water emulsions stabilized by β-lactoglobulin (β-Lg)/pectin complexes. A primary emulsion was produced by homogenizing the sunflower oil contains PX in β-Lg solution (at pH=3.5). Then, the emulsion droplets were stabilized further by coating with pectin as a secondary layer. Four different pectin types including low-methoxyl sunflower pectin (LMSP), high-methoxyl apple pectin (HMAP), high-methoxyl citrus pectin (HMCP), and low-methoxyl citrus pectin (LMCP) were applied for production of double layered emulsion droplets. The entrapping efficiency of PX (%), creaming stability, and mean droplet size (D43) of emulsions were measured. Also, the release trends of PX were determined and fitted with experimental models of zero order, Higuchi, and Pepass. Our results revealed that the emulsions stabilized by β-Lg/high-methoxyl apple and citrus pectins with NaCl had a higher creaming stability and more loading capacity of PX compared to stabilized emulsions by β-Lg/pectin without NaCl. The mean droplet size (D43) of double layered emulsions was increased at higher pectin fraction and were decreased by lower β-lg fraction.

Enhancing Oil Production from Tight Formations Under a Reverse Faulting Stress Regime by Multistage Fracturing

Conventional hydraulic fracturing in multi-layered tight formations under reverse faulting stress regime has not been very promising. This is because of constraints of stress regime and improper modeling of fracture treatment, leading to the development of fracture turning, twisting, premature screen-outs, and shorter fracture length. Thus, this is a treatment design problem, where mathematical parameters relating to fracture geometry suitable for reverse faulting stress regime are not well presented. This article presents the integrated model for pinpoint multistage fracturing, which incorporates in-situ stress regime, constrained fracture geometry, material balance, and conductivity and production model. The model has been applied to multi-layered tight oil formations and benefits have been presented as compared to un-stimulated formations. The result shows about five-fold of production increment.

Analysis of Comparison of Human Meibomian Lipid Films and Mixtures with Cholesteryl Esters In Vitro Films using High Resolution Color Microscopy

The lipid layer of the tears has been studied in vivo using high resolution color microscopy (HRCM). The purpose of these experiments was to gain further insight into the structure of the lipid layer by applying HRCM to in vitro meibomian lipid films. Films of human meibomian lipids, cholesteryl nervonate, cholesteryl palmitate, or their mixtures, were spread on a Langmuir trough. Changes to the films were monitored using HRCM as the films were compressed to different surface pressures. The penetration of albumin into a meibomian lipid film also was studied. Small amounts of meibomian lipids at low pressures formed very thin films estimated to be 5.2 nm thick. Compression caused spots to appear in the films. At higher concentrations, micro lenses were a feature of the film. Cholesteryl nervonate formed a multilayered oil slick that did not change with surface pressure. Cholesteryl palmitate formed a stiff film that collapsed at high compression. Mixtures of cholesteryl nervonate and meibomian lipids showed that they mixed to increase surface pressures above that of the individual components. HRCM also allowed albumin to be seen penetrating the meibomian lipid film. HRCM combined with in vitro surface pressure measurements using a Langmuir trough is useful for modeling meibomian lipid films. The films often resemble the appearance of the lipid layer of in vivo films. The data indicate that the lipid layer might be modeled best as a duplex film containing an array of liquid crystals.

The use of ATR-FTIR imaging to study coated oil capsules

Fourier transform infrared (FTIR) spectroscopic imaging using a large Internal Reflection Element (IRE), also called Attenuated Total Reflection (ATR) crystal, can be used for the identification and localisation of chemical compounds in solid food products. In this study ATR-FTIR imaging, by means of a large area crystal with a contact diameter of 600μm with a linear array detector, was used to elucidate the microstructure of the coating of a sophisticated multi-layered oil capsule with active ingredients (sodium ascorbate, sucrose, gelatine, gum, isoflavone). ATR-FTIR imaging with the aid of principal component analysis (PCA) showed the spatial location of the individual ingredients within the layers and that these ingredients are not uniformly distributed within the layers. By ATR-FTIR imaging it was determined that the layer thickness of the soft central coating layer containing lycopene, sodium ascorbate, sucrose and air is about ∼156μm, the 1st sucrose layer ∼180μm and the gelatine/gum ∼28μm. The latter was confirmed by X-ray microtomography (μCT). The other layers could not be identified by μCT.

Production optimisation and water control in oil/water producing wells using horizontal downhole water sink technology

Water breakthrough and the flow of water towards the perforations of a producing well increase production operation costs and influence overall recovery efficiency. To control water production, a downhole water sink can be used in which a well is completed in both oil and water zones. Water is produced from an interval in water zone, which can result in the same pressure drop below water oil contact (WOC) as the pressure drop created by oil or gas production. This system can reduce water production through oil zone perforations. Water produced from water zone perforations can then be injected in deeper aquifers intervals. This technology can also be implemented in horizontal and multi-lateral wells to further increase hydrocarbon recovery with fewer water problems. This study examines the use of horizontal downhole water sink technology to increase oil recovery. Numerical simulation is performed to optimise oil production and water control in a multi-layered oil reservoir, by optimising the direction of drilling and the downhole water sink method. Different scenarios of drilling direction and horizontal down-hole water sink method are examined to identify the option that provides maximum oil recovery. The simulation results showed that drilling horizontal wells in a north–south direction resulted in higher well productivity, and that wells with significantly more water production problems can be controlled using a horizontal downhole water sink.

Self-organization of Multilayered Oil Droplet in Water

Abstract Dynamic behavior of initially sessile droplets of oleic acid with sodium oleate was investigated in an aqueous buffer solution. The interface of droplet highly fluctuated at pH 9.0 and concomitantly grew a multilayered structure inside of the droplet. Volume change of the droplet suggested the existence of three independent mass-transport processes. This phenomenon was observed under specific conditions of pH and oil composition.

The formation evaluation tool and its application in offshore China

The Formation Evaluation Tool (FET) introduced in the paper represents a new generation of formation evaluation systems developed and manufactured by China Oilfield Services Limited (COSL), CNOOC, using a FET technology transfer from Crocker Research, Australia. The system has been applied successfully in the Bohai Sea and South China Sea. For instance, a multilayered oil and water system has been confirmed with the aid of accurate formation pressure tests, even in very thin beds and edge water reservoirs, overcoming the difficulty of determining this kind of oil-water and gas-water contacts. Moreover, the FET pumping and real-time fluid monitoring function allows acquiring a true sample of formation fluid unpolluted by drilling mud which plays an important role in determining the fluid properties of the target stratum and analyzing the fluid component. The principles and purpose of the Formation Evaluation Tool (FET) will be briefly introduced and successful examples of the application of the technology will be described in detail in this paper.

Application of seismic exploration for direct search of multilayered petroliferous oil fields, Azerbaydzhan

In a multilayered, stratigraphically controlled, tectonically undisturbed deposit of oil-gas, definite seismic expressions of the petroliferous horizons were obtained by the “method of reflected waves,” with certain adaptations. The anomalously high absorption of high-frequency waves was found to be responsible for clarity of the seismic expressions.

Tectonics and oil and gas prospects of Siberian platform provinces

Siberian prognostic reserves of oil and gas are now believed to constitute 40% and 25%, respectively, of U.S.S.R. totals. In the West-Siberian geosyneclise, thickness of hydrocarbon-bearing horizons increases toward the center, in the same direction as bituminosity and content of dispersed organic substance in marine Jurassic and Cretaceous sediments. Multi-layered oil pools are typical of the center; gas and oil pools occur on the periphery of the syneclise. In the Siberian platform, economic accumulations of oil and gas are found in sediments ranging in age from Riphean through Cretaceous. Lower Cambrian and the Underlying Riphean horizons are particularly promising. The Kolyma platfornnal massif, where first indications of oil were discovered in the Permian horizons, remains to be prospected. The close association of gas-petroliferous horizons with perfectly definite facies-zones and the rigorously sustained stratigraphic positions of the latter, as well as demonstrable associations of the hydrocarbon accumulations with their source rocks, leave no doubts as to the organic origins of the Siberian oils.--V. P. Sokoloff.