The pdf file of this paper is in Russian. To purchase the paper in English, order SPE-116955-MS.
The article addresses a large area (a territory 100 km long and 80 km wide) encompassing several oil fields, including South Priobskoye, Chaprovskoye, Kondinskoye, Malokondinskoye, North Kondinskoye and West Kondinskoye. The breakdown of this huge and actually a single oil-and-gas bearing zone consisting of a series of sand lenses and containing 1.5 bln tons of recoverable reserves is rather tentative. The authors of this paper have been working in this area and participated in exploration, investigation and development of numerous fields within the Priobsky-Kondinsky zone. Due to complex geology of clinoform formations, low flow properties of the rocks, wide spacing of exploratory wells and seismic surveys, a number of fields situated in the southern part of the Frolovsky depression were brought into production 15 to 20 years later than expected. A significant engineering breakthrough in oil production occurred due to implementation of massive reservoir fracturing treatments and integrated approach to 3D seismic interpretation. These are the technologies that allowed successful development of low-permeability clinoform productive reservoirs within AS9-AS12 formations in all the fields discovered in this area. As of today, a great amount of 3D seismic surveys were shot in many license areas totaling over 3000 sq km. Production drilling and oil production in actually all the fields within the Priobsky-Kondinsky area involve massive frac jobs. Integrated interpretation of 3D seismic led to surprising results indicating the most complex geology of the Neocomian clinoform reservoirs including both tectonic processes associated with sediment slides, and formation of fans within turbide flows. Thorough insight into spatial position and forecasting of flow and storage properties of each sand body allows efficient drilling and development of low-permeability oil saturated reservoirs in the Priobsky-Kondinsky area.
Rig cost, service company rates and materials costs have gone up significantly in accordance to the oil price. Industry is therefore continuously searching for new technologies to make the drilling of wells safer, more efficient and economical. This paper will explore the possibilities of combining two existing technologies to meet these challenges.
Drilling with casing (DwC) uses standard casing as the drillstring and leaves it in place to case the well. It has a potential of saving of rig time by eliminating drillstring tripping and also minimizing downhole problems. With expandable technology, expanded casing can provide a larger diameter of the production casing. This can increase the well productivity.
Because both technologies have similar operational procedures, they could be combined into one operation. The new concept is to use expandable casing as a drillstring which will be expanded when the target depth is reached.
The conclusion of this analysis is that the drilling with expandable casing concept is possible. However, there are some technological challenges, especially on tools and on the strength of post expansion materials.
The examples analyzed, indicate that we can save 39% of the operation time by running this combined technology. Expenses can be reduced through lowered rig costs and the operational risk can be mitigated. A better understanding of the technology and operational procedures will help to further reduce the risks and make the technology even more acceptable. If this new method succeeds, there will be a high potential for cost savings, higher production rates and better well control.
At present time, a number of oil fields in Orenburg area are at a late stage of development. This leads to oil production decline, with some oil wells becoming so depleted that they have to be shut-in. This paper discusses a joint project to rehabilitate the Sorochinsko-Nikolskoe oil field in order to extend productive time of such wells by identifying candidate wells for horizontal sidetracking. The main goal of the project was the validation of horizontal sidetracking for long-term enhanced oil recovery. To achieve this objective, the joint group needed to select wells suitable for horizontal side tracking and predict both the initial daily oil production rate and cumulative oil production over five years. At the same time, the team had to minimize any risks associated with geological uncertainty. The main criteria for sidetrack selection included an initial oil production rate of more then 75 ton per day, followed by steady production for five years. An integrated approach was used to re-evaluate the development of the oil field. First step of this process was analysis of the oil field development and the identification of bypassed oil reserves to determine zones of interest. The next step was quality control of petrophysical and geological data sets and the analysis of match between initial models and actual production data. The result of this analysis confirmed the need to revise the existing models for a more accurate oil production forecast and to develop a water flooding strategy within the side track zones of interest. The next step was geological modeling based on petrophysical interpretation of porosity and fluid saturation.
Special feature of petrophisical interpretation is new algorithm for calculation of reservoir property. Base of this algorithm is petrophisical equations sort of "core-logging data?? relationship for calculation of reservoir property as a porosity, permeability and fluid saturation. Petrophisical equation for open porosity in target formation was drawn from comparative analysis of core data porosity and neutron porosity. Since this equation was used for processing of all well data in this oil field, time for data processing has been significantly reduced and on the same time, required accuracy of petrophisical value of rock property was achieved. Interpretation results from previous researches on a data set from this oil field do not have a criterion for estimation of fluid saturation type and watersaturation cut-off for pay zone recognition. New algorithm for petrophisical interpretation gives clearly defined criteria for recognition of watersaturated, oil saturated and oil-water saturated pay zones for target carbonate formation. Comparison of log interpretation results based on new algorithm and previous one is shown in Fig. 1. Significantly that, the new interpretation results of oil saturation coefficient depend from porosity and resistivity while quantitative criteria for that calculation were obtained from analyses of acceptable well test results.
The pdf file of this paper is in Russian. To purchase the paper in English, order SPE-114786-MS.
Creating multiple zone stimulations in complex reservoirs presents unique challenges for the completion engineer. Effectively stimulating each individual pay interval using separate fracturing treatments can be costly and time consuming. Historically, efforts to stimulate multiple zones usually consisted of casing fracs with limited entry perforating and using sand plugs to separate zones, or tubing fracs with retrievable bridge plugs and packers. The challenge was to rethink the approach to this technology and develop more cost effective and efficient solutions. Those efforts have resulted in a new approach called pinpoint stimulation.
New pinpoint stimulation methods have resulted in reduced cycle time for operators. This means doing multiple service operations in a single trip to the well. If performed individually, perforating, fracturing, setting isolation plugs, and cleaning out the wellbore for each interval can add days or weeks to a completion, delaying production-to-sales and increasing overall costs. Now, we perforate, fracture stimulate, and clean out with a single trip to the wellsite. Each treatment stage is customized for the intervals treated and many more intervals can be stimulated economically. Pinpoint multistage fracturing is available in 16 different processes for many types of well completions.
In this paper, we present different techniques for a wide variety of applications and provide actual treatment data and results including recent case histories from Russia.
It is important for wells in the Yuzhno-Khylchuyu field (Russian Arctic region) to have sufficient zonal isolation and thermal protection between production casings and the permafrost media because they will initially be produced with high flow-rates. High cement integrity helps prevent the permafrost from thawing therefore alleviating problems associated with the creation of unwanted cross-flows and eventual casing deterioration.
Low-density cement slurry has been used as an alternative to foam cementing because it contains hollow microspheres which help decrease cement thermal conductivity. The use of hollow microspheres in cement blends creates further challenges for engineers with regards to slurry optimization. Special attention is given to slurry properties because the presence of hollow microspheres can influence slurry rheology, increase cement setting time, and act negatively on compressive strength development.
The optimization of slurry design takes all of these parameters into consideration while resolving the problem of heat insulation, thus helping reduce the chance of primary cementing failure over the life cycle of the well.
The optimization of the cement slurry design makes it possible to significantly decrease the initial cement setting time, provide high compressive strength, and resolve the problem of heat insulation.
Preservation of the cement-sheath and heat-insulation properties is one of the most significant challenges during development of cement slurry design for permafrost intervals ("Cement Blends can be tested for Arctic Environments??).
There are several ways to resolve this issue. Using hollow microspheres is the most cost-efficient method. However, there are a number of issues with hollow microspheres that can negatively influence cement slurry: reduced cement-sheath strength, increased cement setting time, and deterioration of rheological parameters. These issues can cause mixing slurry to be more difficult.
This paper provides a summary of the methods used to prepare optimized cement slurry with hollow microspheres for use in permafrost intervals.
Oil production at high flow-rates has been connected to permafrost thaw problems, resulting in a need for development of an optimized cement slurry to provide good heat-insulation between a casing and formation since the temperature of extracted hydrocarbon fluid is 57°C.
Permafrost at theYuzhno Khylchuyuskoye field is represented by the Quaternary system. The depth is 185 m. The icy layers are at 0 to 10 m below icy rocks. The standard well construction at the Uzhno Khylchuyuskoye field is: 640-mm conductor in 910-mm openhole to 30 m, 340-mm surface casing in (406.4 mm) openhole to 650 m, and 244.5-mm production casing in 311.1-mm hole to 3000 m. The 630-mm conductor casing covers the icy layers from 0 to 30 m (Fig. 1).
At the development stage of the Yuzhno Khylchuyuskoye field, the design institute prepared a thermal engineering analysis based on thermal conductivity coefficients of the materials used in well cementing (Fig. 2). According to this analysis, the problem with permafrost thawing was resolved by using a slurry that contains hollow microspheres at a concentration of 20% BWOC.
The company used a cement slurry containing gypsum for cementing in permafrost for long periods of time. Initially, the original cement slurry, with a density of 1.47g/sm³, containing 20% BWOC of hollow microspheres and 160% BWOC of gypsum-based additives was used for cementing the 640-mm conductors. In this case, G cement was used.
An error in software, science, or data has an equal opportunity to yield incorrect results. Imagine using a computer or a software program that randomly gave the incorrect answer 30% of the time. Productization of hardware and software has given us products of much higher quality. This paper presents a methodology, DQM, for productizing the data.
Treating data as a product is a fundamental requirement in any data quality process. In this paper we apply productization to upstream E&P data and refer to it as making data suitable for a specific process. Treating data as a product forces the definition of data requirements, in a similar manner as we are accustomed to define requirements for other products. The degree that the data product meets these requirements defines the quality of the data product. Productization of data thereby yields a measurable
definition of data quality.
This paper shows how productization of data yields a productivity centric definition of data quality. It further shows that Data Quality can be decomposed into five dimensions:
By applying an extended Design for Six Sigma (DFSS) approach, we show that data quality can be measured using the traditional sigma score. Our studies show that for organizations that do not utilize a data quality process the overall quality is less then three sigma, resulting in a resource waste of more than 30%. We further present findings regarding how organizations are adopting the new data product paradigm along with the overall impacts and lessons learned.
The pdf file of this paper is in Russian. To purchase the paper in English, order SPE-115710-MS.
Previous studies showed that injection of water and gas as water alternating gas (WAG) process or simultaneous water and gas (SWAG) process can improve the sweep efficiency. Therefore, oil recovery from depleted reservoirs can be enhanced by combined injection of water and gas. However, SWAG process compare to WAG process is less known. Investigation of factors that affect on miscible SWAG injection is the aim of this study. For this purpose, a three-dimensional finite-difference reservoir simulator is used. Methane (as gas) at minimum miscibility pressure (MMP) is injected into an under-saturated reservoir which contained typical North Sea oil. Water and gas are injected at fixed rates by two separate horizontal wells. For more sweep efficiency and increase the distance gas and water travel before segregation, gas is injected at the bottom of reservoirs. For water, different locations of injection are tested and the effect of water injection location is studied. We also investigate the effect of water to gas injection rate ratios, well models, and reservoir heterogeneity on sweep efficiency and oil recovery.
Today, there is a clear tendency towards structure and quality deterioration of reserves. One of the reasons lies in low initial oil saturation (about 0.45-0.55 for the regions of Western Siberia). Average residual oil saturation is equal to some 0.3 (in this case displacement efficiency - 0.4). With displacement efficiency being that low, final oil recovery factor will be just over 25% even if the reservoir sweep factor can be increased to about 70%.
In the mid-XX century the method of oil field development using gas injection which theoretically allows 100% displacement was developed.
The paper discusses two technologies for implementation of gas methods used in oil field development. - alternating gaswater injection (AGWI) and water-gas stimulation (WGS) in which combined injection of displacement agents (gas and water) is used. It describes the principle of operation and features of special equipment developed on the basis of a multi-purpose booster compressor unit operating under the principle of a single-stage "compressor with hydraulic seal??.
The paper presents procedures for realization of AGWI & WGS, as well as practical developments allowing to prevent typical problems which occur in the process of field equipment operation when pumping high pressure gas.
Actual results of WGS introduction in one of the JSC "RITEK?? fields are presented and technological benefits of the process are assessed using 3D geologic-hydrodynamical simulation data.
Although the design and manufacturing technology of submersible rotary pump units (SRPU) are constantly improving, for the last few years no fundamental technological
solutions for the drives of these units have been offered. Efficiency of submersible asynchronous electric motors which conditions both energy consumption and service life has virtually never been changed within many years. Today, it has become obvious that opportunities of further efficiency increase for standard electric motors of PED type (submersible) are virtually exhausted. During operation of SRPU in specific modes the resource of PED and the unit as a whole significantly decreases.
The definition of oil displacement mechanism is one of major questions in problem of reservoir processes: or as mixed oilwater flow, when oil and water phase relative permeability (kro and krw) of water flood zones are specified; or as piston flow, when takes place frontal drive of oil by stream of approaching water.
Phase relative permeability for water and oil are usually defined on the basis of learning filtering of oil-water mixtures through a core. Just on the basis of such experiments the curves of phase relative permeability to oil and water are performed, which then used in the different design documents and projects of field development.
At the same time it is known, for example, that using modern methods of engineering inclusive reservoir simulation model are large difficulties at history matching with applying of such relative permeability curves of filtered fluids. Frequently forced variation of parameters of filtering at history matching results in concurrence of calculated and actual indexs to development at final parameters of filtering much distinguished from source, obtained in laboratory conditions.
It is necessary to mark also, that in the literature last years many papers have appeared that the core is a poor material that only on its basis to plan field development because of unrepresentative of coring, as a result of which it does not mirror property of all reservoir system; high created gradients of stresses at studies in laboratory conditions as contrasted to actual; strictly oriented directivity of flow of fluid through a core with impossibility of an estimation of anisotropy of formations on permeability and etc.
In a paper the features of extraction of oil reserves on some fields of Western Siberia are reviewed. Is shown, that as a whole on fields there are complex processes of fluid flow, where are formed as regions of water inrushes with consequent catastrophic watering out of individual wells, and zones of oil displacement with waterless wells, working a long time, and recovery of reserves in such zones much greater, than initial oil reserves in drained areas of these wells. It is impossible to explain by widespread assumptions about influencing reformative phase relative permeability or complex heterogeneity of oil reservoir. Formed zones of oil displacement to durable waterless operation of wells, as a rule, are connected with frontal drive. The examples of operation of some horizontal wells with high oil recovery factor (more than 0.5) in area of their
drainage. The results of numerous production and injection well testing and conducting of hydrolistenings testify to such nature of water-oil displacement.
The concrete offers on rational field development methods are made, when the piston condition of water-oil displacement is organized predominantly.