Horizontal Wells 2017

This paper presents the technological solutions to problems of cementing wells on the fields of PJSC “LUKOIL” in Western Siberia, related to the absorption of cement slurries due to low fracturing pressure, of high risk of annular flow due to minimum size of bridges between water and the part of oil formation. Also resolved an issue associated the cementing of wells with using thermo-gas treatment of the formation (TGT).

The presented technological solutions with the special cements allowed to a large extent solve the above problems and improve the quality of cementing on the fields of PJSC “LUKOIL” in Western Siberia.

The geologic-geophysical support while drilling of horizontal wells using 3D seismic data is performed in addition to real-time geosteering. The aim of this work is provision the optimal trajectory for the well’s horizontal section. The example of Yuri Korchagin and Vladimir Filanovsky oil fields is considered in the article. Target objects are the oil-saturated Lower Cretaceous Neokomian terrigenous deposits. In addition to base 3D geological model a detailed seismic-geological model is built based on detailed seismic interpretation. The results of the geologic-geophysical support while drilling of horizontal wells are presented to the Monitoring and Decision-making Centre in a timely manner. Involving detailed interpretation of seismic data in geosteering process can reduce the uncertainty of geosteering model and clarify the actual position of the wellbore. In addition to the basic structural-tectonic model it helps to allocate low-amplitude tectonic disturbances, local structural elements of reservoir, which are usually not included in standard geological model, but can produce a risk of complications during drilling.

Offshore fields development requires applying high tech decisions in the very limited and restricted environment. Drilling of long horizontal wells is one of the most efficient ways to maximize oil recovery while minimizing number of wells. And quality of the well placement in such horizontal wells becomes essential for reaching planned production levels. Real time geosteering plays key role in making horizontal drilling successful.

Applicability of different geosteering tools is dependent on the geological specifics of each particular formation. Key parameters to assess efficiency of geosteering tools are: thickness of the reservoir, structural features, presence of layers with high resistivity/density contrast etc. And it is completely different situation if there are faults on the way of the well. Presence of several faults drastically reduces ability of geosteering tool to predict rock properties and geological boundaries and makes proactive trajectory adjustment very difficult.

In this presentation we will share our experience of planning and execution of the horizontal well drilling in the area of the field which is heavily faulted. Proactive approach in integration of all existing data and precise planning allowed achieving all geosteering objectives and successfully place the well in target interval.

Construction of boreholes with horizontal completion in complex geological environments calls for the application of high-tech geophysical complexes for logging while drilling (LWD). The first Russian LWD telemetry system has been created. This paper is dedicated to the development of an interpretation framework for the equipment in question. We have performed an analysis of the results of using computational algorithms and software for data processing and interpretation. We have also conducted numerical simulation and inversion of electromagnetic log data with regard to solving geosteering problems. The algorithms and software have been tested on practical logs.

The real-time interpretation of Extra-Deep Azimuthal Resistivity LWD measurements resulted in the extended reservoir characterization of the lithological heterogeneity of the Fort McMurray Formation, including clean sand facies, inclined heterolithic stratification (IHS) facies, and mud-filled channel facies. This lithology was compounded by fluid heterogeneity within the reservoir, including irregular Oil-Water Contacts (OWC), partial reservoir charging, lean zones and top gas zones.

The increase in actual exploited oil reserves (quantitative), was estimated at more than 50 percent compared to the projected reserves exploited by the planned wellbore trajectory.

This new formation evaluation approach was proven while drilling four horizontal producers in the unconsolidated oil reserves with high reservoir heterogeneity, which stressed the need for operators to fully understand their subsurface in order to maximize oil recovery.

This new logging-while-drilling approach offers an opportunity to better understand the oil reservoir, which ultimately leads to increased production performance of Oil Sands projects. Utilization of this technology in future projects will fundamentally change the efficiency of drilling and completion practices within the oil industry.

The article describes ultra-deep reservoir mapping tool – GeoSphere implementation for extended reach well geosteering in Sakhalin offshore. A number of conclusions were made about mapping capabilities of the technology in formation environment on Lebedinskoye field. The results could be used for special geosteering objectives including landing the well without a pilot hole drilling, reservoir boundaries mapping, sub seismic faults, and stratigraphic features interpretation.

Continental deposits require confident trends for predicting the distribution of geobodies in highly heterogeneous reservoir. Each new pilot well can significantly change the concept of reservoir architecture and consequently horizontal well targets. Dynamic and flexible drilling strategy allowing taking into account the uncertainties is the key factor of successful geosteering process. The research describes approaches for optimal well placement in condition of permanently renewed and updated geological knowledge about the reservoir.

The usage of modeling techniques allows to optimize the materials and construction of the neutron well logging apparatus and synthesized the recorded signal. This study focuses on modeling the construction of PNL device for determining the spatial position of hydraulic fractures in three-dimensional space. We used mathematical modeling by Monte Carlo method. PNL logs were synthesized, and it allowed to restore position of hydraulic fracture. The difference between angels simulated and the resulting equaled 3 degree, which confirms the possibility of using this technique.

Currently, true dip computation using borehole images is typically based on the routines developed in the 1960s. This approach was formulated for wireline images in vertical wells where boundaries assumed to be planar surface, and could be presented as a sinusoid on the image log.

A different scenario applies for LWD images in horizontal wells. Boundaries can be observed for tens of meters or greater. Within these distances planar geological boundaries are rarely found. The corresponding image response is not an ideal sinusoid shape. Further, it is unlikely that wellbore has constant inclination and azimuth while penetrating geological boundary, introducing explicit inaccuracy in 2-dimensional true dip calculation. The variable depth of investigation for radioactive LWD tools causes additional uncertainty. Another challenge is the human bias in sinusoids manual definition that is a considerable issue in geological applications.

The developed workflow relies on 3-dimensional approach to determine bedding geometry. Boundaries described with contours on 2-dimensional image, which are then transferred to 3-dimensional coordinates. The method forms set of contours where relevant formation boundaries are selected using fuzzy logic. Special noise removal routine is part of the method. Current study highlights advantages of the proposed method over the conventional dip picking workflow.

Salt plugging is quite common issue for oil and gas reservoirs in Eastern Siberia fields.

Salt plugging reduces reservoir properties to the state of no-pay. Formation evaluation of gas reservoirs in presence of salt in pore space is quite problematic and can’t be performed with standard triple-combo set of measurements. It requires additional measurements like Spectroscopy and Sigma. The paper describes the utilization of LWD Sigma (Neutron Capture Cross-section) measurement to assess and evaluate zones of salt plugging in gas reservoirs. It is crucial that Sigma log is acquired while drilling to avoid invasion and also facilitate formation evaluation in horizontal well.