Work performed as a Seconded at Carrizo & Oil USA 

By Sourav Bhardwaj 

Oil India Limited acquired 20% interest in Carrizo Oil & Gas Inc liquid rich shale assets,

i.e. Niobrara Asset, in the Denver–Julesburg (D-J) Basin in Colorado, USA. The Purchase and

Participation Agreement (PPA) with Carrizo was signed on 4th October 2012 and the acquisition

became effective from 1st October 2012.

On Oct’ 2014 joined as a secondee to Carrizo Oil & Gas to gather the knowledge and to

understand the unconventional reservoir as well as operational activities related to the

unconventional field at the USA. The following work has been carried out during my whole

tenure:

1. Performed all geological work using Petra Software (iHS) of Niobrara area under the

guidance of Mr. Paul Fears (Mentor), Geologist Carrizo Oil & Gas.

Petra (iHs):

Petra is a cost-effective software solution for managing, manipulating and visualizing

integrated geological, geophysical and engineering data. Geologists, engineers,

technicians, and analysts use Petra for exploration, exploitation, infill drilling, reserves

analysis, unconventional plays, production analysis and more. With Petra, quickly

visualize results using mapping, cross-sections, seismic interpretations, log plots, cross-

plots, production and reservoir analysis, and 3D visualization.

Petra enables to:

a. Expedite drilling decisions with shorter cycle times

b. Integrate large IHS well, production and log data sets

c. Quickly define reservoirs and prospects

d. Focus on analysis rather than map-making

e. Analyze mergers, acquisitions, and divestitures

2. Prepared several maps viz. Thickness, Resistivity, Structural, Saturation, Porosity etc.

and regional correlation of wells based on the data available in the area.

Fig. Thickness Map

Fig. SoPhiH map

Fig. Resistivity map

Fig. Correlation of the wells

3. Expedite drilling decisions with shorter cycle times using the geo-steer software (SES) of

Carrizo operated wells. SES is horizontal and directional well bore drilling software for pre-

spud well planning with geologic model data integration through landing and 3D technical

geosteering / stratigraphic interpretation while drilling or post drilling. Includes 2D/3D

directional well planning methods, minimum curvature directional survey calcs, Technical

Hole Deviation (THD) calcs, THD logs, steering guidance from patented Fuzzy Logic control

technology, and advanced visual geosteering interpretation tools using LWD (gamma

radiation, resistivity, etc.)

Geosteering:

Geosteering, in general, is drilling a horizontal wellbore that ideally is located within or near

preferred rock layers. As interpretive analysis performed while drilling or after drilling,

geosteering determines and communicates a wellbore's stratigraphic depth location in part

by estimating local geometric bedding structure. Early geosteering was performed mostly

with interpretation from cuttings samples, paper well logs and maps, and rough sketches.

Modern geosteering normally incorporates multiple dimensions of information, including

insight from quantitative correlation methods. Ultimately, today's geosteering methods

provide an explicit approximation to the location of nearby geologic beds in relation to a

wellbore or coordinate system, and as such, help to explain rock/wellbore completion and

subsequent oil/gas/water/frac fluid-flow observations from or into rock.

Technical geosteering is a computational signal-mapping task. Timely and depth-accurate

logging while drilling formation evaluation (LWDFE) data is transformed—using a geometric

location estimate of a marker bed—to plot on a representative stratigraphic type log. An

acceptable “fit” suggests a good estimate of the marker bed location.

a. Gamma Ray

The most common LWDFE measurement applied to technical geosteering is omni-

directional gamma ray. Gamma ray is chosen because of its relatively insensitive signal

response to varying pore fluids, rock porosity, rock permeability, and circumferential

borehole quality. Another favourable gamma ray attribute is a short depth of investigation

(e.g., 4-6 inches); with less rock “seen” by the tool there is less chance for signal

complication.

In oil and gas geosteering applications, the measured depth (MD) frequency of gamma ray

data is typically 0.5 or 1 ft, which enables fault-crossing recognition. Some operations rely

on focused gamma ray measurements (e.g., borehole high side and low side readings) to

either outright drive technical geosteering or to augment interpretations relying primarily on

omni-directional gamma ray measurements.

b. 3D Curved World

What complicates the software engine of technical geosteering is addressing the fact that

both the well path (known-location) and the payzone (unknown-location) simultaneously

change and curve in three-dimensional (3D) space. A two-dimensional (2D) technical

geosteering analysis—one based on the vertical section for example—inherently suppresses

resolution and introduces distortion, especially with ‘3D’ wells and or ‘2D’ wells with thin pay

zones.

c. 3D Technical Geosteering

In 2006, Stoner Engineering LLC developed a 3D technical geosteering methodology that

eliminates the shortcomings of 2D analysis. Two new geologic terms resulted from this work:

3DStratBlock and relative stratigraphic depth.

A 3DStratBlock (3DSB) is a planar surface that mathematically represents the 3D location

of a geologic marker—usually the top of the pay zone. The target well path is at some offset

distance parallel to this marker. A 3DSB is defined with a true dip, a true dip direction

azimuth, map coordinates corresponding to an MD along the actual well path, and a control

point true vertical depth (TVD).

Fig. Geosteering of the well

4. Based on wells data (viz production, logs etc.) quickly define reservoirs and prospects of

unconventional fields.

5. Focus on analysis rather than map-making. The following main analysis term is used:

i) Estimated ultimate recovery (EUR) approximates the quantity of oil or gas that

is potentially recoverable or has already been recovered from a reserve or well.

ii) IP (Initial Production) of the well used for analysis of productivity of the area.

iii) Decline rate analysis is important, that gives the idea how fast the reservoir is

going to decline (Time Rate Analysis).

6. Analyze mergers, acquisitions, and divestment of the different Assets.

7. Acquire complete information (Geology, Reservoir properties & operators) of Oil plays in the

United States under the different basins. Detail analysis provided to Carrizo.

8. Monitor and evaluate production performance of the Carrizo, Whiting & Noble wells.

9. Evaluate financial performance for assets and company portfolios using GEM Modules.

Understand the effect of cost overruns and project delays on asset valuation. Export data into

in-house workflows and systems for further analysis.

10. Prepared prospect map of all basins of USA using Carrizo IHS license through Enerdeq

Browser. All wells information viz, Drilling, completion, production, operator information etc.

have been used for better understanding of unconventional reservoirs time to time.

IHS Enerdeq Browser:

IHS Enerdeq provides online access of well data and the subscription-based US Well,

Production and Land data, including well completions and production entities:

a. Allocate resources to analysis rather than research

b. Consolidate data management into a single source

c. Streamline workflows to evaluate acreage and generate prospects

d. Assess competitive position and oil well production

e. Identify field outlines and oilfield service opportunities