UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 11-K

(Mark One)
x	ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
For the fiscal year ended December 31, 2013
	TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
For the transition period fromto
Commission File Number 001-10924

A. Full title of the plan and the address of the plan, if different from that of the issuer named below:

Clayton Williams Energy, Inc. 401(k) Plan & Trust

Six Desta Drive - Suite 6500

Midland, Texas 79705

B. Name of the issuer of the securities held pursuant to the plan and the address of its principal executive office:

Clayton Williams Energy, Inc.

Six Desta Drive - Suite 6500

Midland, Texas 79705

CLAYTON WILLIAMS ENERGY, INC.

401(k) PLAN AND TRUST

TABLE OF CONTENTS

	Page
Report of Independent Registered Public Accounting Firm	1
Statements of Net Assets Available for Benefits - December 31, 2013 and 2012	2
Statement of Changes in Net Assets Available for Benefits - Year Ended December 31, 2013	3
Notes to Financial Statements	4
Supplemental Schedule:
Schedule H, Line 4i - Schedule of Assets (Held at End of Year) - December 31, 2013	S-1

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

The Plan Administrator

Clayton Williams Energy, Inc.

401(k) Plan and Trust

Midland, Texas

We have audited the accompanying statements of net assets available for benefits of the Clayton Williams Energy, Inc. 401(k) Plan and Trust (the “Plan”) as of December 31, 2013 and 2012, and the related statement of changes in net assets available for benefits for the year ended December 31, 2013. These financial statements are the responsibility of the Plan’s management. Our responsibility is to express an opinion on these financial statements based on our audits.

We conducted our audits in accordance with the auditing standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

In our opinion, the financial statements referred to above present fairly, in all material respects, the net assets available for benefits of the Clayton Williams Energy, Inc. 401(k) Plan and Trust as of December 31, 2013 and 2012, and the changes in net assets available for benefits for the year ended December 31, 2013, in conformity with accounting principles generally accepted in the United States of America.

Our audits were performed for the purpose of forming an opinion on the basic financial statements taken as a whole. The supplemental schedule H, Line 4i, schedule of assets held for investment purposes as of December 31, 2013, is presented for the purpose of additional analysis and is not a required part of the basic financial statements, but is supplementary information required by the United States Department of Labor Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. The supplemental schedule is the responsibility of the Plan’s management. The supplemental schedule has been subjected to the auditing procedures applied in the audit of the basic financial statements and, in our opinion, is fairly stated in all material respects in relation to the basic financial statements taken as a whole.

/s/ Hein & Associates LLP

Dallas, Texas

June 12, 2014

CLAYTON WILLIAMS ENERGY, INC.

401(k) PLAN AND TRUST

STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS

	December 31,
	2013		2012
ASSETS:
Investments, at fair value:
Stable value fund	$	4,450,366	$	4,121,352
Mutual funds	27,861,827		21,700,884
CWEI common stock	13,611,822		6,779,154
	45,924,015		32,601,390
Sponsor contribution receivable	131,314		167,212
Other assets	1,456		630
Total assets	46,056,785		32,769,232
LIABILITIES	—		—
NET ASSETS AVAILABLE FOR BENEFITS AT FAIR VALUE	46,056,785		32,769,232
Adjustment from fair value to contract value for stable value fund	(57,546)		(120,039)
NET ASSETS AVAILABLE FOR BENEFITS	$	45,999,239	$	32,649,193

See accompanying notes to these financial statements.

2

CLAYTON WILLIAMS ENERGY, INC.

401(k) PLAN AND TRUST

STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS

Year Ended December 31, 2013

ADDITIONS TO NET ASSETS ATTRIBUTABLE TO:
Dividends and interest	$	970,051
Net appreciation in fair value of investments	12,071,837
Contributions:
Participant contributions	2,515,682
Sponsor contributions	1,655,361
Total contributions	4,171,043
Total additions	17,212,931
DEDUCTIONS FROM NET ASSETS ATTRIBUTABLE TO:
Distributions	3,912,851
Administrative fees	12,527
Total deductions	3,925,378
NET INCREASE IN NET ASSETS AVAILABLE FOR BENEFITS AT FAIR VALUE	13,287,553
NET ASSETS AVAILABLE FOR BENEFITS AT FAIR VALUE:
Beginning of year	32,769,232
End of year	$	46,056,785

See accompanying notes to these financial statements.

3

CLAYTON WILLIAMS ENERGY, INC.

401(k) PLAN AND TRUST

NOTES TO FINANCIAL STATEMENTS

1.    Description of Plan

The following description of the Clayton Williams Energy, Inc. (the “Company”) 401(k) Plan and Trust (the “Plan”) is provided for general information purposes only. Participants should refer to the Plan agreement for a more complete description of the Plan’s provisions.

General

The Plan, as amended and restated, is a defined contribution plan established by Clayton Williams Energy, Inc. (the “Company” or “CWEI”) under the provisions of Section 401(a) of the Internal Revenue Code (“IRC”), which includes a qualified deferred arrangement as described in Section 401(k) of the IRC, for the benefit of eligible employees of the Company who become entitled to participate in the Plan. Employees who have 90 days of service and are age 21 or older are eligible to participate in the Plan. The Plan is subject to the provisions of the Employee Retirement Income Security Act of 1974, as amended (“ERISA”).

Plan Administration

The Plan is administered by the Company. ADP Retirement Service, Inc. (“ADP”) is the Plan’s recordkeeper and holds the Plan’s assets. ADP is also the Trustee and is responsible for accepting funds, managing them and distributing them to beneficiaries.

Contributions

The Plan requires that the amounts of all participant and Company contributions comply with limitations established by the IRC. Subject to these limitations, participants may contribute to the Plan up to 100% of pre-tax annual compensation, as defined by the Plan, and the Company, in its sole discretion, may provide a matching contribution equal to a percentage of participants’ contributions. The Company makes matching contributions equal to 100% of participants’ contributions, limited to 6% of compensation. The Company may also make discretionary profit-sharing contributions to the Plan which are allocated to participants’ accounts based on each participant’s compensation as a percentage of total compensation.

Vesting

Participants are fully vested in their contributions and the earnings thereon. The Plan has been established as a safe-harbor plan; therefore, participants are fully vested in Company matching and discretionary contributions upon entry into the Plan.

Benefits

Upon termination of service due to death, disability or retirement, participants may request and receive a lump-sum distribution in an amount equal to the value of the vested interest in their respective accounts. Participants may also receive hardship withdrawals of their accounts, subject to certain limitations, as defined by the IRC.

Participant Accounts

Individual accounts are maintained to reflect each participant’s allocated share of the Plan’s income, the Plan’s administrative expenses, the Company’s contributions, and the participant’s contributions. Allocation of investment income is based on participant account balances.

4

CLAYTON WILLIAMS ENERGY, INC.

401(k) PLAN AND TRUST

NOTES TO FINANCIAL STATEMENTS

Investment Options

As directed by participants, the Plan purchases units of participation in twenty distinct investment portfolios sponsored and administered by ADP. In addition, the Plan makes participant-directed investments and matching contributions in the Company’s common stock. Under the Plan, participants are allowed to transfer funds between any investment options, including the Company stock fund.

Administrative Expenses

At its discretion, the Company may pay all or any portion of administrative expenses on behalf of the Plan. Administrative expenses paid by the Company were not significant.

2. Summary of Significant Accounting Policies

Basis of Accounting

The financial statements and supplemental schedule are prepared on the accrual basis of accounting.

Payment of Benefits

Benefit payments are recognized when paid. Benefits due to participants who have elected to withdraw from the Plan but have not been paid are deducted from net assets available for benefits. At December 31, 2013 and 2012, there were no amounts allocated to withdrawing participants.

Investment Valuation and Income Recognition

Investments of the Plan are stated at fair value. Securities traded in public markets are valued at their quoted market prices. Purchases and sales of securities are reflected on a trade-date basis. Changes in the market value of investments from one period to the next, combined with realized gains and losses based on differences between revalued costs and market value of investments on the trade date are recognized as net appreciation or depreciation in fair value of investments in the accompanying statement of changes in net assets available for benefits.

Interest income is recorded as earned on the accrual basis. Dividend income is recorded on the ex-dividend date. Reinvested income is reflected as additions to the cost basis of investments.

Estimates and Assumptions

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires the Plan Administrator to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of changes in net assets available for benefits during the reporting periods. Actual results could differ from those estimates.

5

CLAYTON WILLIAMS ENERGY, INC.

401(k) PLAN AND TRUST

NOTES TO FINANCIAL STATEMENTS

3. Investments

The following presents investments that represent 5% or more of the Plan’s net assets as of December 31, 2013 and 2012:

	December 31,
	2013		2012
Putnam Stable Value Fund	$	4,450,366	$	4,121,352
WFA Premier Large Company Grade A	4,182,686		(a)
Baron Growth Fund	3,932,712		2,515,382
JPM Value Adv Fund Select	3,701,825		(a)
T. Rowe Rice Retirement 2020	(a)		1,711,843
Growth Fund of America-R3	(a)		3,273,925
Oppenheimer Value Fund-N	(a)		3,215,512
Templeton Foreign-A	(a)		1,837,334
Clayton Williams Energy, Inc. common stock	13,611,822		6,779,154

(a) Investment did not exceed 5% of more of the Plan’s net assets.

The Stable Value Fund is a collective investment trust organized in order to provide participants with a stable, fixed-rate return on investment and protection of principal from changes in market interest rates.

The Stable Value Fund’s rate to be credited to participants is set at the start of the contract and resets on a quarterly basis. The average yield of the entire Stable Value Fund based on actual earnings was 1.86% and 2.36% at December 31, 2013 and 2012, respectively. The average yield of the pooled separate accounts based on the interest rate credited to participants was .86% and 1.44% at December 31, 2013 and 2012, respectively. To calculate the required yield, the amount credited to participants for the last day of the period is annualized and divided by the fair value of the investment portfolio on that date.

The Stable Value Funds are in the Statements of Net Assets Available for Benefits at fair value in the investments total, and adjusted to contract value in determining the net assets available for benefits.

	As of December 31, 2013
	Rating S&P/ Moody’s	Investment at Fair Value		Wrap Contract at Fair Value	Adjustment to Contract Value
Putnam Stable Value Fund	AA/Aa2	$	4,450,366	—	$	(57,546	)
	As of December 31, 2012
	Rating S&P/ Moody’s	Investment at Fair Value		Wrap Contract at Fair Value	Adjustment to Contract Value
Putnam Stable Value Fund	AA/Aa2	$	4,121,352	—	$	(120,039	)

6

CLAYTON WILLIAMS ENERGY, INC.

401(k) PLAN AND TRUST

NOTES TO FINANCIAL STATEMENTS

During 2013, the Plan’s investments (including gains and losses on investments bought and sold, as well as held during the year) realized a net appreciation as follows:

Mutual funds	$	5,301,662
Stable Value Fund	(62,493)
CWEI common stock	6,832,668
	$	12,071,837

4. Fair Value Measurements

Financial Accounting Standards Board ASC Topic 820 (“ASC 820”), Fair Value Measurements, establishes a framework for measuring fair value. That framework provides a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy under FASB ASC 820 are described below:

Ÿ Level 1	Inputs to the valuation methodology are unadjusted quoted prices for identical assets or liabilities in active markets that the Plan has the ability to access.
Ÿ Level 2	Inputs to the valuation methodology include:
	ŸQuoted prices for similar assets or liabilities in active markets;
	ŸQuoted prices for identical or similar assets or liabilities in inactive markets;
	ŸInputs other than quoted prices that are observable for the asset or liability;
	ŸInputs that are derived principally from or corroborated by observable market data by correlation or other means.
	If the asset or liability has a specified (contractual) term, the Level 2 input must be observable for substantially the full term of the asset or liability.
Ÿ Level 3	Inputs to the valuation methodology are unobservable and significant to the fair value measurement.

The asset’s or liability’s fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Valuation techniques used need to maximize the use of observable inputs and minimize the use of unobservable inputs.

Following is a description of the valuation methodologies used for assets measured at fair value. There have been no changes in the methodologies used at December 31, 2013 and 2012.

• Common stock: Valued at the closing price reported on the active market on which the individual securities are traded;

• Mutual funds: Valued at the net asset value (“NAV”) of shares held by the Plan at year-end;

• Stable Value Fund: Valued at the net fair value per unit of the fund’s underlying investments.

7

CLAYTON WILLIAMS ENERGY, INC.

401(k) PLAN AND TRUST

NOTES TO FINANCIAL STATEMENTS

The methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while the Plan believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date.

The following table sets forth by level within the fair value hierarchy, the Plan’s assets at fair value as of December 31, 2013 and 2012:

	Assets at Fair Value as of December 31, 2013
	Level 1		Level 2		Level 3		Total
Mutual Funds
Income funds	$	1,752,525	$	—	$	—	$	1,752,525
Growth and income funds	6,900,012		—		—		6,900,012
Growth funds	11,204,194		—		—		11,204,194
Aggressive growth funds	8,005,097		—		—		8,005,097
Common Stock
Oil and gas extraction industry	13,611,822		—		—		13,611,822
Stable Value Fund
Putnam stable value	—		4,450,366		—		4,450,366
Total assets at fair value	$	41,473,650	$	4,450,366	$	—	$	45,924,016

	Assets at Fair Value as of December 31, 2012
	Level 1		Level 2		Level 3		Total
Mutual Funds
Income funds	$	1,944,144	$	—	$	—	$	1,944,144
Growth and income funds	5,334,005		—		—		5,334,005
Growth funds	8,649,320		—		—		8,649,320
Aggressive growth funds	5,773,415		—		—		5,773,415
Common Stock
Oil and gas extraction industry	6,779,154		—		—		6,779,154
Stable Value Fund
Putnam stable value	—		4,121,352		—		4,121,352
Total assets at fair value	$	28,480,038	$	4,121,352	$	—	$	32,601,390

8

CLAYTON WILLIAMS ENERGY, INC.

401(k) PLAN AND TRUST

NOTES TO FINANCIAL STATEMENTS

5. Party-in-Interest Transactions

As of December 31, 2013 and 2012, the Plan’s following party-in-interest investments which were either administered by the Trustee or holdings of CWEI.

	2013		2012
DWS RREEF Real Est Secur-A	$	639,897	$	611,225
DWS S&P 500 Index Fund-S	928,704		641,742
CWEI common stock	13,611,822		6,779,154

The Plan paid $12,527 in 2013 and $4,129 in 2012 to ADP for administrative fees.

6. Tax Status

ADP obtained a favorable determination letter from the Internal Revenue Service on March 31, 2008, stating that the prototype plan, which was adopted by the Plan in 2004, is a qualified plan under the IRC. The Plan has been amended since this time and management has not received an updated determination letter but believes the Plan is in compliance with the applicable requirements of the IRC to remain tax-exempt.

7. Plan Termination

Although it has not expressed any intent to do so, the Company has the right under the Plan to terminate the Plan subject to the provisions of the ERISA.

* * * * * * *

9

SUPPLEMENTAL SCHEDULE

CLAYTON WILLIAMS ENERGY, INC.

401(k) PLAN AND TRUST

Schedule H, Line 4i - Schedule of Assets (Held at End of Year)

EIN: 75-2396863

December 31, 2013

Identity of Issuer	Description of Investment	Cost	Current Value
Putnam Investments	Putnam Stable Value Fund	**	$	4,450,366
Loomis Sayles	Loomis Sayles Bond - Admin Income	**	434,896
Baron Capital, Inc.	Baron Growth Fund	**	3,932,712
JP Morgan	JPM Value Adv Fund Select	**	3,701,825
Allianz Global Investors Distributors, Inc.	Allianz NFJ Small Cap Value-R	**	1,196,975
Wells Fargo	WFA Premier Lg Co Gr A	**	4,182,686
* DWS Investment Company	DWS RREEF Real Est Secur-A	**	639,897
* DWS Investment Company	DWS S&P 500 Index-S	**	928,704
Franklin Templeton Investments	Templeton Foreign-A	**	2,235,512
Pimco Total Return Fund	Total Return Fund-A	**	1,317,629
John Hancock Funds	J Hancock Balanced Fund-R4	**	1,669,764
T. Rowe Price Mid Cap Growth	Mid Cap Growth Fund-R	**	1,245,299
T. Rowe Price Investment	T. Rowe Price Mid Cap Value-R	**	1,145,680
T. Rowe Price Investment	T. Rowe Price Retirement Income-R	**	170,315
T. Rowe Price Retirement	T. Rowe Price Retirement 2015-R	**	1,088,053
T. Rowe Price Retirement	T. Rowe Price Retirement 2020-R	**	2,083,551
T. Rowe Price Retirement	T. Rowe Price Retirement 2030-R	**	472,969
T. Rowe Price Retirement	T. Rowe Price Retirement 2040-R	**	1,022,207
T. Rowe Price Retirement	T. Rowe Price Retirement 2050-R	**	393,153
* Clayton Williams Energy, Inc.	Common Stock	**	13,611,822
* Clayton Williams Energy, Inc.	Participant Loan	**	1,456
			$	45,925,471

* Indicates each identified person/entity known to be a party-in-interest for the year ended December 31, 2013.

** Historical cost information is omitted as permitted for participant-directed transactions under an individual account plan.

S-1

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the trustees (or other persons who administer the Plan) have duly caused this annual report to be signed on its behalf by the undersigned hereunto duly authorized.

CLAYTON WILLIAMS ENERGY, INC.

401(k) Plan & Trust

(Name of Plan)

By:	Clayton Williams Energy, Inc.
	Plan Administrator

Date:	June 12, 2014	By:	/s/ Mel G. Riggs
			Mel G. Riggs
			Executive Vice President and Chief
			Operating Officer

CLAYTON WILLIAMS ENERGY, INC.

401(k) PLAN AND TRUST

EXHIBIT INDEX

Exhibit
Number	Description of Exhibit
23	Consent of Independent Registered Public Accounting Firm