Geodynamic Monitoring with GNSS: Tracking Deformation on Kazakhstan Oilfields

Geodynamic monitoring is the systematic instrumental observation of ground-surface deformation above a producing oil or gas field. As fluid is withdrawn from the reservoir, pore pressure declines, the reservoir compacts, and the ground surface above the deposit subsides. On Kazakhstan oilfields with decades of production history, cumulative subsidence can reach metres, while annual rates are measured in centimetres. Oilfield deformation monitoring turns those movements into hard numbers: it quantifies subsidence and horizontal displacement cycle by cycle, and it warns operators, in time, of risks to wells, pipelines and surface facilities.

This article is written for the technical staff of oil and gas operators — surveyors, survey-department heads, and facility-integrity engineers — who need to set up geodynamic monitoring on fields in the Mangystau Region and along the Kazakhstan Caspian coast. It explains why deformation monitoring matters, which methods and equipment deliver it, how often cycles should run, and exactly what the client receives.

What Geodynamic Monitoring Is

Geodynamic monitoring is the observation of ground-surface deformation across a producing field, carried out to detect and forecast induced ground movement. The primary driver of that movement is fluid withdrawal — oil, gas, or formation water — from the productive reservoir. Falling reservoir pressure compacts the reservoir rock, and the compaction propagates upward as subsidence that reaches the day surface as a broad depression known as a subsidence bowl.

Deformation monitoring resolves movement into three components:

• Vertical subsidence — the downward movement of the surface above the withdrawal zone. This is the principal and most hazardous form of deformation on oilfields.
• Horizontal displacement — in-plane movement of surface points, characteristic of the flanks of the subsidence bowl, where horizontal strain concentrates.
• Tilt and structure deformation — derived quantities that are critical to the stability of individual assets such as storage tanks, pipe racks, and wellheads.

Observations are not one-off; they run in cycles. The first cycle — the “zero cycle” — fixes the baseline position of every observation point. Each subsequent cycle is compared with the zero cycle and with the previous one, and it is that comparison that reveals the deformation process over time.

Why Oilfields Need Geodynamic Monitoring

Deformation monitoring is not a paperwork exercise; it is a risk-management tool for a long-life producing asset. Its core objectives are as follows.

Well integrity. Differential subsidence imposes shear loads on casing strings. Casing shear or collapse within a subsiding interval is a severe failure that can cost the well. Monitoring identifies zones of intense subsidence so the operator can adjust the withdrawal regime before casing is compromised.

Pipeline integrity. Flowlines and trunk pipelines crossing a subsidence bowl accumulate longitudinal and bending stresses. Knowing the actual subsidence profile along the route lets the operator assess remaining pipeline life and plan compensating measures such as re-supporting or re-routing.

Surface-facility stability. Tank farms, flare stacks, pipe racks, and pump-station buildings founded on collapsible soils require settlement control. This is especially relevant around Aktau and the coastal belt, where induced subsidence is superimposed on the settlement of saline, collapsible ground.

Forecasting. A multi-year observation series supports a predictive subsidence model, allowing operators to build allowances into the design of new wells and facilities before deformation reaches them.

Subsoil-use compliance. The Code of the Republic of Kazakhstan “On Subsoil and Subsoil Use” places mine-surveying provision — including observation of ground-surface movement — among the obligations of the subsoil user. The Rules for Conducting Mine-Surveying Works set requirements for organising observation stations and for observation frequency at deformation-prone sites. The specific scope and frequency are fixed in the field’s mine-surveying project and mining-geological documentation, so any monitoring programme is agreed with the subsoil user and the supervisory authority rather than assumed.

Methods of Geodynamic Monitoring

Accuracy and reliability come from combining several geodetic methods. No single method covers every requirement, so an oilfield monitoring station is normally a complex observation network.

The Geodynamic Network of Benchmarks and Points

The foundation of monitoring is a network of permanently fixed points — benchmarks — covering the field and its zone of expected influence. Points are set for the long term: ground and deep benchmarks for vertical observation, and GNSS points with forced-centring devices for horizontal observation. A subset of points is established outside the deformation zone; these serve as the reference (datum) points and are treated as stable.

Periodic Static GNSS Observations

Static GNSS observation is used to determine both horizontal and vertical displacements of the network points. At each point, a receiver records a long occupation session; the baselines between points are then processed in the office. Static positioning delivers stable sub-centimetre accuracy across the whole field and is particularly effective where the spacing between points is large — a defining condition on Kazakhstan oilfields, where control points are sparse and baselines run long.

High-Precision Geometric Levelling

For the most accurate determination of vertical settlement specifically, Class II geometric levelling is used. It is the most precise method for measuring height differences and can reliably capture subsidence at the level of a few millimetres per cycle — a resolution beyond satellite methods. Levelling runs tie the working benchmarks of the observation network back to the datum benchmarks outside the deformation zone.

Comparing Cycles Against the Zero Cycle

The output of any method is the comparison of point coordinates and heights in the current cycle against their values in the zero and previous cycles. The differences yield the displacement values from which movement schedules, graphs, and subsidence maps are built. It is the repeatability of measurement — the same method, the same points, cycle after cycle — that makes results comparable.

Equipment for Geodynamic Monitoring

The credibility of monitoring depends directly on the class of instruments used and their metrological certification. TOO GeoProGlobal carries out deformation monitoring with the following set of equipment.

The South Galaxy G9 GNSS receiver is used to build and re-observe the geodynamic network by static positioning. The receiver is multi-constellation (GPS, GLONASS, Galileo, BeiDou), which is decisive for a stable solution on the long baselines forced by a sparse control network. Its stated static accuracy is 2.5 mm + 0.5 ppm — sufficient to resolve horizontal and vertical displacement of network points between cycles.

The Leica LS10 digital level, used with an invar bar-code staff, delivers high-precision settlement determination by Class II levelling. With the invar staff, the instrument achieves an error of the order of 0.3 mm per kilometre of double run, allowing millimetre-scale benchmark subsidence to be tracked confidently from one cycle to the next.

The Leica TS06 Plus total station, with 5″ angular accuracy, is used to determine the horizontal displacement of individual points and deformation targets on structures, and for angle-and-distance measurement where GNSS is unusable — for instance, close to tall steelwork that screens the satellite signal.

Equipment	Role in monitoring	Key specification
GNSS South Galaxy G9	Geodynamic network; horizontal and vertical displacement (static)	2.5 mm + 0.5 ppm; GPS/GLONASS/Galileo/BeiDou
Leica LS10 digital level	High-precision settlement (Class II levelling)	0.3 mm/km with invar staff
Leica TS06 Plus total station	Horizontal displacement; deformation targets on structures	5″ angular accuracy

All instruments undergo regular calibration; the use of uncalibrated equipment is not permitted and leads to documentation being rejected by the mine-surveying supervisory authorities.

How Often to Run Monitoring

Observation frequency is one of the central questions in planning a monitoring programme. There is no universal answer: cycle frequency is set by the mine-surveying project and depends on several factors.

Typical frequency for a field in a stable production stage is two to four cycles per year. A half-yearly or quarterly interval is enough to separate the subsidence trend from seasonal ground movement.

Factors that drive frequency:

• Withdrawal intensity. The higher the production rate, the faster reservoir pressure falls and the more intense the subsidence — so cycles are run more often.
• Development stage. Deformation is more active during the growing and plateau production stages than in decline.
• Active deformation. Where intense or differential subsidence is detected, observation is intensified — up to monthly on critical sections.
• Project and regulator requirements. The final programme is fixed in the field’s mine-surveying design documentation.

The zero cycle must be run before, or in the early phase of, intensive development. Without a correct zero cycle, every later observation loses its basis for comparison.

What the Client Receives

After each cycle, and after a series of cycles, the subsoil user receives a documentation package fit both for engineering decisions and for submission to the mine-surveying supervisory authorities.

Displacement schedules — tables of the vertical and horizontal displacement of every point relative to the zero and previous cycles, with an accuracy assessment.

Subsidence graphs by cycle — time series of subsidence at representative points, showing the rate and dynamics of the process at a glance.

Subsidence maps and diagrams — contour plans of the subsidence bowl across the field, localising the zones of greatest deformation.

Stability conclusion and recommendations — an engineering assessment of the monitored assets, findings on the character and rate of deformation, and recommendations on the withdrawal regime, on protecting facilities, and on the future observation frequency.

All documentation is prepared in a single system of coordinates and heights tied to the State Geodetic Network of Kazakhstan, and is signed by a certified specialist.

Specifics of Mangystau Region Oilfields

Deformation monitoring on the oilfields of the Mangystau Region and the Caspian coast carries a set of specifics that raise the bar for the contractor.

Saline, collapsible soils. The coastal belt around Aktau and the Mangyshlak Peninsula is built of saline soils prone to collapse on wetting. Induced subsidence above the reservoir is superimposed on soil deformation, so interpreting the results demands that these components be separated rather than lumped together.

Remoteness and desert terrain. Fields are frequently 200–400 km from Aktau, in desert and semi-desert terrain. The benchmark network must be established and maintained far from any settlement, which calls for self-contained expedition work and careful mobilisation planning.

A sparse control network and long baselines. State Geodetic Network points in the remote parts of Mangystau are few and often lost. Tying the observation network to the state coordinate system relies on long GNSS baselines, and it is precisely for a stable solution on these that a multi-constellation receiver of the South Galaxy G9 class, running extended static sessions, is needed.

Benchmark survival. In open desert terrain, benchmarks are vulnerable to damage and burial. Points are set robustly, and their survival is checked at the start of every cycle.

TOO GeoProGlobal is based in Aktau and has experience on the oilfields of the Mangystau Region, including knowledge of the local coordinate systems used by operators and of the access procedures for licensed subsoil-use blocks.

Summary Table of Methods

Method	What it measures	Accuracy	Typical frequency
Class II geometric levelling	Vertical benchmark settlement	~0.3–2 mm per cycle	2–4 times per year
Static GNSS observation	Horizontal and vertical displacement of network points	2.5 mm + 0.5 ppm	2–4 times per year
Total-station measurement	Horizontal displacement; deformation targets on structures	5″ angular	Per cycle, or more often on critical assets

Conclusion

Geodynamic monitoring is the technical foundation of safe, long-life field development. Fluid withdrawal inevitably drives ground subsidence, and without systematic deformation monitoring neither the integrity of wells and pipelines can be assured nor the mine-surveying obligations of subsoil use can be met. A combination of Class II geometric levelling, static GNSS observation, and total-station measurement — run in cycles and compared against the zero cycle — gives the operator an objective picture of the deformation process, from displacement schedules through subsidence maps to a stability conclusion.

For the oilfields of the Mangystau Region, with their saline soils, remoteness, and sparse control network, the quality of monitoring depends directly on the contractor’s experience and the class of equipment. TOO GeoProGlobal delivers oilfield deformation monitoring in Aktau and across Mangystau with a set of the South Galaxy G9, Leica LS10, and Leica TS06 Plus — from establishing the observation network to issuing the stability conclusion.

To discuss a monitoring programme and cycle frequency for your field, get in touch through geoproglobal.kz. We will prepare a proposal that reflects your development stage and the requirements of the mine-surveying project.