RubberMat Co 4 inch Mat Analysis

California Bearing Ratios vs Drilling Rig Platform Performance

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Preface (RubberMat Co)

This document contains information based on the finite element analysis of the RubberMat Co produced 4 inch Mat. The results represent well over a hundred hours of computer processing time conducted over an array of simulations. Genmark has done its best, with the information provided, to ensure accurate & precise results. Material models for the mats have been developed over time during the course of previous projects with slight improvements during each iteration.

Mat Material Properties Table

			Thermoplastic Resin	Steel Mesh
Modulus of Elasticity	E	ksi		31910
Shear Modulus	G	ksi		11850
Yield Strength	σy	psi		30020
Tensile Strength	σt or σc	psi	680	50040
Poisson’s Ratio	u	unitless	0.360	0.280

Soil properties were determined using California Bear Ratio (CBR) guidelines. CBR strength tests yield a value for comparing load bearing capacity of a sub grade material to that of well graded crushed stone. The American Association of State Highway and Transportation Officials (AASHTO) published the Mechanistic Empirical Pavement Design Guide (MEPDG) in 2008. AASHTO MEPDG uses the formula below to convert CBR to resilient modulus (MR) (in psi), which is itself an approximation of modulus of elasticity.

M_R ≅ 2555 × CBR^0.64

Soil Material Properties Table (assumed to be temperature independent)

California Bearing Ratio	CBR	unitless	1	2	3	4	5	6	7	8	9	10
Soil Poisson’s Ratio	u	unitless	0.350	0.350	0.350	0.350	0.350	0.350	0.350	0.350	0.350	0.350
Soil Density (est)	r	lb/cu in	0.048	0.055	0.062	0.069	0.077	0.084	0.091	0.098	0.105	0.112
Soil Modulus of Elasticity	E	psi	2555	3980	5160	6200	7160	8050	8880	9670	10430	11160

At the request of RubberMat Co, loading produced by three different rigs were to be considered in the analysis. The major task in processing the rig information was to identify the location and magnitude of the greatest ground pressure produced by the various modular components used in the drilling process. The rig loads to

be analyzed were based on a Major Drilling Rig Supplier (specifically for Drilling Rig Sizes: SINGLE, DOUBLE and TRIPLE load rating were used ). Unfortunately, the rig information provided was not accurate. As a result, major assumptions and estimations were made during process of establishing relative ground pressures produced by different rig components. The results for DOUBLE rig are noted to be the most accurate of the three rigs and can be considered quantitatively correct.

The analysis of DOUBLE rig showed that the actual drilling assembly (consisting of the substructure, mast assembly, drill floor, drawworks, etc.) coupled with the static hook load, was easily the most intensely loaded component of all the rig’s modules. The mat analysis was based on the ground pressure produced at the underside of the frame rails of the substructure.

In order to complete this project for the other two rigs (SINGLE and TRIPLE) Genmark estimated the weights of the respective drilling assemblies by comparing the static hook load of DOUBLE rig to the weight of its drilling assembly structure, and created a ratio using the hook loads of each rig compared with that of DOUBLE rig. The results generated for SINGLE and TRIPLE Rigs are accurate, however they lack precision due to the missing weight information. As a result,these weights cannot be considered quantitatively correct or precise.

It is the opinion of Genmark that the information generated in the analysis of the ground pressure loads produced by SINGLE and TRIPLE Rigs are useful guidelines for the purpose of selecting the number of required mat layers based on site soil conditions (CBR). If better information is forwarded to Genmark in the future, it is possible to re‐perform the analysis and amend this document to include any changes mandated by the new data.

Typical Mat Loading (10 soils x 3 Rig Loads = 30 tests)

4 inch Mat Assembly ‐ Complete

4 inch Mat Assembly ‐ Thermoplastic Resin is partially removed

4 inch Mat Assembly ‐ Thermoplastic Resin is fully removed

4 inch Mat Assembly ‐ Thermoplastic Resin and One Layer of Mesh removed

Typical Mat Loading and Mesh

Introduction

This document was produced at the request of RubberMat Co and represents an intensive analysis of the RubberMat Co 4 inch mat and its behavior under varying loads and soil conditions. Well over a hundred hours of computer processing time was required to produce these results. The analysis was based on material specifications provided by RubberMat Co. The rig loads to be analyzed were based on a Major Drilling Rig Supplier (specifically for Drilling Rig Sizes: SINGLE, DOUBLE and TRIPLE).

Soil properties were determined using California Bear Ratio (CBR) guidelines. Material models simulating the properties of soil with California Bearing Ratios of 1 through 10 were tested with anticipated maximum loads produced by the three respective drilling rigs.

As complete data was provided for DOUBLE Rig, this enabled Genmark to produce precise results. Results for SINGLE and TRIPLE Rigs are based on estimated module weights, and while accurate, these results could be skewed if the actual component weights are much different from those used in the analysis.

Rig Specifications

SINGLE RIG

Static Hook Load: 111200 daN (250000 lb)
Drilling Assembly Weight: 265400 lb (Estimated)
Total Load Through Substructure: 515400 lb (Estimated)
Substructure Skid Beam Contact area ‐ 103.6 sqft (Estimated)
Contact Pressure = 515400 lb / 103.6 sqft = 4975 lb/sqft = 34.5 psi

DOUBLE RIG

Static Hook Load: 333600 daN (750000 lb)
Drilling Assembly Weight: 796250 lb
Total Load Through Substructure: 1546250 lb
Substructure Skid Beam Contact area ‐ 155.4 sqft (Provided)
Contact Pressure = 1546250 lb / 155.4 sqft = 9950 lb/sqft = 69.1 psi

TRIPLE RIG

Static Hook Load: 444800 daN (1000000 lb)
Drilling Assembly Weight: 1061700 lb (Estimated)
Total Load Through Substructure: 2061700 lb (Estimated)
Substructure Skid Beam Contact area ‐ 155.4 sqft (Estimated)
Contact Pressure = 2061700 lb / 155.4 sqft = 13267 lb/sqft = 92.1 psi

Loading Summary

Single Rig	P	psi	34.5
Double Rig	P	psi	69.1
Triple Rig	P	psi	92.1

Looking at the above numbers the weights of the drilling assemblies are large without adding in the static hook load. The only other component to rival this weight is the mud tanks, which can weigh an estimated 350000 to 400000 lb when fully loaded (which have not been verified and may vary from rig to rig). When the static hook load is added to the drilling assembly weight, the full load through the substructure is clearly the largest of all modules.

RubberMat Co 4 inch Mat: Performance Summary for 3 different rigs and 10 different CBR

4 inch mat is consists of internal reinforcement (Double Layer of Steel Mesh 100 x 100 x 7) and a main outside body (Thermoplastic Resin). Based on extensive analysis, Genmark was capable to individually evaluate stresses in different mat materials and compare it to maximum allowable stresses.

Allowable Deflection	δ	in	0.375
Allowable Stress Resin	σall_r	psi	410
Allowable Stress Steel	σall_s	psi	18084

Allowable Deflection and Stresses in different Mat Materials

Full Mat Deflection Summary (10 CBR's and 3 Loads)

Displacement vs. California Bearing Ratio, 4 inch Mat (Full Mat)

Typical Mat Deflected Shape

Based on the above result, mat deflections are good for the imposed conditions, for all CBR values and for all loading condition. Maximum Deflection encountered during Tripple Rig Loading on CBR 1 soil and it is 0.1727 inch < 0.375 inch maximum allowable.

Thermoplastic Resin Stress Summary (10 CBR's and 3 Loads)

Stress vs. California Bearing Ratio, 4 inch Mat ( Thermoplastic Resin)

Based on the above results, thermoplastic resin stresses are good for the imposed conditions for:

All stresses that are below 410 psi ‐ are acceptable (blue color in the table)
All stresses that are above 410 psi ‐ are not acceptable (yellow color in the table)

Thermoplastic Resin Stresses (typ)

Steel Mesh Stress Summary (10 CBR's and 3 Loads)